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FIRST BOOK 



IN 



CHEMISTRY. 

FOR THE USE OF 

SCHOOLS AND FAMILIES. 
BY WORTHINGTON HOOKER, M.D., 

PEOFESSOB OF THE THEOEY AND PRACTICE OF MEDICINE IN YALE COLLEGE, AUTHOR OF 

"human physiology, 11 "child's BOOK OF NATURE," 
"natural history, 1 ' etc. 

Jfllustrateir bg ©ngratnng^, 
f 

NEW YORK: 

HARPER & BROTHERS, PUBLISHERS, 

FRANKLIN SQUARE. 

18 6 2. 



C<L+ -t^t^ts/- / 0' / b u *L_ 



By Dr. Worthington Hooker. 



The Child's Book of Nature. For the Use of Families and Schools ; intend- 
ed to aid Mothers and Teachers in training Children in the Observation of Nature. In Three 
Parts. Past I. Plants. — Paet II. Animals. — Pakt III. Air, Water, Heat, Light, &c. Illus- 
trated by Engravings. The Three Parts complete in one vol. Small 4to, Cloth, $1 25 ; Sepa- 
rately, Cloth, 50 cents each. 

Natural History. For the Use of Schools and Families. Illustrated by nearly 

300 Engravings. 12mo, Cloth, $1 00. 

First Book in Chemistry. For the Use of Schools and Families. Illustrated 
by Engravings. Square 4to, Cloth. 



Entered, according to Act of Congress, in the year one thousand eight hundred and sixty-two, by 
If AfiPEB & Beothers, in the Clerk's Office of the District Court of the Southern District of New York. 



* Z / M. *- 



PREFACE. 



The idea of this book was suggested by a lady, who is a stranger 
to me, in a letter, a portion of which I will quote here. " I can not 
tell you how much pleasure I have had in teaching the Child's Book 
of Nature to my little daughter. In giving my own opinion of that 
work I am also expressing the opinion of several other mothers of 
my acquaintance, who agree with me in pronouncing it the very best 
book of the kind which we have ever found. It is so plain and sim- 
ple in its arrangement that any child of common capacity can learn 
it with ease and remember it well. The subjects upon which it 
treats are of a kind to interest all children, and the pleasant way in 
which you bring them forward is sure to awaken their powers of 
observation and comparison, and, better still, to lead them c through 
Nature up to Nature's God.' It seems to me that an elementary 
book on Chemistry, upon the same plan, would be interesting to chil- 
dren, especially if they could have some simple and safe experiments 
which they might try for themselves," 

Soon after receiving this letter I put the matter to a test in the 
following manner. I selected a few of those school-rooms in the pub- 
lic schools of New Haven in which the scholars were from eleven to 
thirteen years of age. I visited these rooms from time to time, talk- 
ing to the pupils for half an hour on chemistry, without trying any 



yi PREFACE. 

experiments, but illustrating the subject largely from common every- 
day phenomena. At each visit I questioned them upon what I had 
told them at the previous visit, and allowed them to ask me ques- 
tions. In this way I found out what they could understand, and 
what they wanted to know about chemistry. I was surprised to see 
how much of this science was within the reach of their capacity, and, 
at the same time, could be made very interesting to them. During 
all this time I jotted down my results, and at length put them into 
the shape in which they now appear, so that the book was almost 
literally made in the school-room. I may add that nearly the whole 
has been subjected to the examination of one of the teachers whose 
rooms I visited, a lady to whom I am indebted for many valuable 
suggestions. 

This book can be readily comprehended by pupils of average ca- 
pacity of twelve or even eleven years of age, especially if they have 
gone through with my Child's Book of Nature, which it is intended 
to follow. At the same time it is fitted for older scholars, to whom 
the subject of chemistry is entirely new. 

I need hardly say that there must be carefulness in experimenting, 
and that some of the experiments described in this book should be 
tried only by teachers, or by pupils under their supervision. 

This book is to be followed by three other books for the next 
higher grade of pupils. They are to be under one title, Science for 
the School and the Family. Part I., Natural Philosophy. Part II., 
Chemistry. Part III., Mineralogy and Geology. 

WOETHINGTON HOOKER. 



CONTENTS. 



CHAPTER PAGE 

I. THE CHEMIST 9 

IT. OXYGEN 15 

ILL NITROGEN 22 

IT. AQUA FORTIS AND THE LAUGHING GAS 27 

V. CARBON 31 

VI. CARBONIC ACID 37 

vii. carbonic acid — Continued 42 

VIII. THE AER 50 

IX. HYDROGEN 58 

X. COMBUSTION 67 

XI. GAS-MAKING AND GAS-BURNING 73 

XII. STRIKING FIRE 81 

XHI. ANIMAL HEAT 86 

XTV. IRON-RUST, POTASH, SODA, AND LIME 92 

XV. METALS AND THEIR OXYDS 99 

xvi. metals and their oxyds — Continued. 105 

XVII. ALLOYS AND AMALGAMS Ill 

XVIH. ACIDS 116 

XIX. SALTS 125 

XX. CARBONATES 129 

XXI. SULPHATES, NITRATES, AND ACETATES 137 

XXII. SHELLS, CORALS, AND BONES 144 

XXIII. GLASS AND EARTHENWARE 150 



Vlll CONTENTS. 

CHAPTER PACK 

XXIV. CHLORINE, BLEACHING, AND COMMON SALT 156 

XXV. CHLORIDES, IODIDES, BROMIDES, AND SEA-WATER 162 

XXVI. SOLUTION AND CRYSTALLIZATION 169 

XXVII. CHEMICAL AFFINITY 177 

XXVIII. WOOD 185 

XXIX. STARCH AND SUGAR 191 

XXX. GLUTEN 198 

XXXI. FERMENTATION 204 

XXXII. VEGETATION 211 

XXXHI. CHEMISTRY OF ANIMALS 219 

XXXIV. CONCLUDING OBSERVATIONS 224: 



THE 



CHILD'S BOOK IN CHEMISTRY. 



CHAPTER I. 

THE CHEMIST. 



What the chemists do. Their discoveries. 

IN" this book you are to learn about Chemistry. But what is 
Chemistry ? you will ask. This I will explain to you in part 
in this chapter ; but you can not understand fully what it is till 
you become well acquainted with what this science can show you. 

You see represented in the frontispiece a large room with a 
great many different kinds of vessels, and instruments, and appa- 
ratus. There are several persons, chemists, engaged in trying 
experiments. Their object is to find out of what things differ- 
ent substances are composed, and what effects will be produced 
when they are mixed together. 

The chemists have discovered a vast many things which will 
surprise you. Each of the substances that you see all about you 
you are in the habit of thinking of as being one thing. The chalk 
with which you mark on the blackboard you think of as chalk, 
and that is all. But the chemist has discovered that chalk is 
made of three things put together. One of them is a gas as thin 
as air. In fact, it is a gas that forms a part of the air which you 



10 



THE CHEMIST. 



Composition of -water. 



Experiment. 



breathe. Another is carbon, or charcoal. Yes, the dark charcoal 
makes a part of the white chalk ; but it is not dark now, because 
it is united with other things. The other thing in chalk is a 
metal. A gas, charcoal, and a metal, then, all three very unlike 
each other, make chalk. 

Then there is water. Water, simple water, that surely, you 
will say, must be one thing. People used to think so — old phi- 
losophers as well as common people and children. But the chem- 
ists found out that it was not so. Water is composed of that 
same gas that is in the chalk, united with another gas with which 
they sometimes fill balloons. These two gases are uniting to- 
gether to form water continually all around you. This is going 
on in every fire and every light that you see burning. In the 
flame that you see, whether it be flame of wood, or candle, or gas 
or burning fluid, these two gases are busy uniting together to 



Fig. 1. 




form water. You do not see the water, for as 
fast as it is formed it flies off into the air. It 
makes a part of the water in the air which is so 
finely divided up that you can not see it, as I 
have explained in Chapter XIX. of the Third 
Part of the Child's Book of Nature. But you 
can catch this water that is formed in the flame 
as it flies off, and make it to be seen. There are 
many ways in which you can do this. Here is 
one represented in Fig. 1. There are ice and 
salt in the bowl, the object of which is merely 
to make the bowl very cold. The bowl is held 
so far above the candle that the soot will not 



THE CHEMIST. 11 



Catching water from flame. What it is to decompose. 

gather upon it. Now the finely divided and heated water, as it 
flies up, strikes against the cold bowl, and is condensed upon it. 
A large drop of water therefore hangs, as you see, from the bot- 
tom of the bowl, fairly caught and brought to view. Considerable 
water can be caught in this way. 

You can do the same thing with a silver spoon or a piece of tin, 
if it be cold. Held over a candle or lamp, dew will gather upon 
it. You do not catch as much water in this way as with the bowl 
of ice and salt, because the surface is not so cold, and is smaller. 
You can not only catch the water that flies off from flame, but 
Fig. 2. you can shut it up, as you see in Fig. 2. The 

candle here is placed under a glass jar, and 
the water first makes the glass dim, but soon 
gathers so much as to trickle down its sides. 
The air outside keeps the glass cool enough 
to make the experiment succeed. You can 
try this experiment with any glass jar, but 
you must remember to put some little bits 
of wood under the edge, as you see in the 
figure. If you do not, the candle will soon go out, for reasons 
that I will explain to you in another chapter, and there will be 
but little water formed. 

The water is composed of two gases. Now when the chemist 
takes some water and separates one of the gases in it from the 
other, we say that he decomposes the water. He does just the op- 
posite of what is done in flame, for there the two gases, as I have 
told you, unite together to form water. So, when he separates the 
ingredients of chalk from each other, he decomposes the chalk. 




12 THE CHEMIST. 



Why you can understand Chemistry and be interested in it. 



I shall tell you, in other parts of this book, much more particu- 
larly about these and a great many other wonderful things. 

I suppose that you have thought that you are too young to 
know any thing about Chemistry, and that none but older and 
wiser persons can understand about it. But this is not so. There 
are a vast. many things in Chemistry that you can understand as 
well as the wisest man on earth. I shall try to select those things 
only which you can understand and which you will be interested 
to know, and leave all the rest for you to learn hereafter, when 
you get farther on in years and knowledge. 

Chemistry will be interesting to you because it tells about so 
many things that you see every day. I suppose that you have 
been in the habit of thinking that the chemist is engaged in find- 
ing out only about things that have hard names, and that you 
have nothing to do with. But it is far otherwise. Very many 
things that he can tell you about are the commonest of all things. 
I have already spoken of chalk and water. The little that I have 
told you about their composition interests you, and you will be 
much more interested when I come to tell you more particularly 
about them. Then there is the air that you breathe — you will 
like to know about that. The chemist can tell you what part of 
the air keeps you alive, and how it does it. You will be sur- 
prised to learn that some of the air is continually becoming a part 
of your body, your flesh and bones, and that some of your body 
is all the time turning into air and flying off all around you. But 
so it is, as I shall by-and-by show you. 

Chemistry will tell you how fires and lights burn. You will 
find that there is a great deal of chemistry in so common a thing 



THE CHEMIST. 13 



Common things explained by Chemistry. 



as a candle. There is enough to talk about for hours. The most 
distinguished chemist in England lately delivered six lectures to 
a young audience in London on the " Chemical History of a Can- 
dle," and 'they have been published, making a book of over 200 
pages. 

Chemistry will tell you what it is that makes bread rise, and 
how it is that the grain from which it is made is fitted in growing 
to nourish your body. 

It will tell you how wine is made from grapes and other fruits, 
and explain what that is in the making of cider and beer which 
is called working. It will explain, too, the making of vinegar. 

It will tell you how soaps are made, and explain the way in 
which Ay operate in cleansing clothes and other things from 
dirt. 

It will tell you about the making of different paints and dyes. 

About these and very many other common things Chemistry 
can tell you a great deal that will interest you, and will be of use 
to you as you grow up to be men and women. And you can 
know much about these and other subjects, young as you are, 
that the wisest chemists did not know fifty years ago, for chemists 
have discovered many facts that were not known then. 

You hear a great deal about the experiments that the chemists 
try. In this book I shall tell you of many experiments that you 
can try for yourselves. You can try them with bottles and tubes 
that you can buy with a very little money, and many of them you 
can try even with what you can pick up about house at your own 
homes by exercising a little contrivance. 

But you will not need to do even this to be interested in Chem- 



14 THE CHEMIST. 



Chemical experiments which you try every day. 



istry, because there are things happening before you continually 
that illustrate the subject. There are experiments, as we may 
say, going on all around you and even within you ; and you have 
only to look and to think, to get Chemistry out of the commonest 
things. Every time that you rub a match, or set fire to gas, or 
a candle, or wood, or strike fire with your heel, you try a chem- 
ical experiment. Every time that you draw a breath, you make 
chemical work for your lungs. Every time that you eat, you set 
a going in your stomach some of the chemical operations that 
the chemist in his laboratory sets a going in some of his queerly- 
shaped glass vessels. And your body is kept warm, as I shall 
show you in one of the chapters of this book, by a sort of chemical 
fire in you — a fire without a flame. 

Questions, — What do chemists do ? Of how many things is chalk composed ? 
What are they ? Which of them are solid substances ? Why is not the charcoal 
dark in the chalk ? What did all people use to think about water ? What have the 
chemists found out about it ? Tell about the formation of water in flame. Why do 
you not see the water that is formed? How can you catch the water as it flies off? 
Tell about catching it with a spoon. Tell about catching it from a candle under a 
jar. What is decomposition? Why can you expect to understand much about 
chemistry in studying this book ? Why will chemistry be interesting to you ? What 
are some of the things that chemistry will show you about air? What is said about 
the chemistry of a candle? What can the chemist tell you about bread? What 
other things will Chemistry explain to you ? What is said about experiments ? 



OXYGEN. 15 

Why words are hard. What you have to do with oxygen. 



CHAPTER II. 

OXYGEN. 

Oxygen. That is a hard word, you will say. Why hard? 
Simply because it is new, and you do not understand what it 
means. "V^hen I have told you what oxygen is, and related to 
you the interesting facts about it, the word will be as easy to you 
as any other word of the same length of which you know the 
meaning. The names of many of your acquaintances would be 
hard words to you if they were not the names of those that you 
know. Now I expect to make you as well acquainted with oxy- 
gen as you are with any of your friends, and then it will be quite 
as easy a name to you as Joseph, or Caroline, or Elizabeth. There 
are many words which you use every day that are much longer 
than oxygen, such as amusement, dissatisfaction, experiment, etc. ; 
but they are easy to you, because you know what they mean, and 
you are familiar with them. And so, when you have gone through 
this book, oxygen and other terms now new to you, and therefore 
hard, will be easy to you, because you have become familiar with 
their meaning and use. 

Though you are not yet acquainted with oxygen, you have a 
great deal to do with it. Indeed, you could not have done with- 
out it at any moment since you were born. Every time that you 
draw a breath you take some of it into your lungs, for there is 
some of it in the air. If what there is of it in the air should be 



16 OXYGEN. 



Oxygen part of your food. Qualities of gases. 

taken out of it, you would die as quickly as you would if you 
were under water. 

This oxygen is part of the food, the nourishment of your body. 
It does not, it is true, go into your stomach, but still it is just as 
necessary food for your body as the food that you swallow. It 
is food that goes into the lungs, and the lungs must have it or 
you will die. 

The food that you put into your stomach you can do without 
for some time. You can live without it even for days ; but the 
lung-food you must have every minute. 

The food that goes into you by your lungs helps to make up 
the solid part of your bodies — your bones, muscles, skin, etc. But 
it is not solid when it goes in. It is a gas. There are a great 
many different kinds of gases or airs. The air that you breathe 
is a mixture of these gases. The gas that we burn is a very dif- 
ferent gas from that we have in the air. If you live in a village, 
perhaps you never saw gas burning from a gas-burner. But you 
see gas burning every day when you see a flame of any kind, 
whether it comes from wood, or coal, or a candle, or a lamp. The 
oil or tallow is changed into gas before it burns. What we call 
flame is burning gas. When wood or coal is burned, all except 
the ashes that are left goes off into the air, and burns as it goes. 

Most gases have no color, and you can look through them as 
you look through glass. You are always looking through gases, 
for the air, as I have told you, is a mixture of three gases. You 
can not see the air, and so you can not see any gas that has no 
color. For example, if a gas-burner be left open without being- 
lighted, you can not see the gas coming out, although you can 



OXYGEN. 17 



Oxygen the most abundant substance in the world. 



smell it. The colorless gases are said then to be perfectly trans- 
parent, like clear glass, because objects are seen or appear through 
them, trails being the Latin for through. 

I shall tell you about many different gases in this book, but now 
I must speak particularly of oxygen. 

Oxygen, besides being a part of the air, is a part of almost 
every thing that you see. It forms a large part of all the water 
in the world. As I have already told you, it is in your skin, and 
muscles, and bones, and every part of your bodies, and is the 
most important part of the blood that runs in your veins and ar- 
teries. It is in all animals and all plants. It makes a part of the 
ground beneath your feet, and even the solid rocks are made in 
part of oxygen. This gas is the most abundant substance in the 
world, and so it is more in use than any other substance. 

It may seem strange to you that so light and thin a substance 
as gas is can make a part of any solid, as flesh or bone. But you 
see every winter a liquid become solid, for ice is solid water. Now 
this same water, that is sometimes liquid and sometimes solid, is 
sometimes also as thin as air or gas. There is always some wa- 
ter in the air, even when it seems to be very dry ; and as in the 
clear air that seems so dry there is no water to be seen, the water 
must be as thin as the air itself. It is no more strange that oxy- 
gen gas can become a part of a solid, than that this water, as thin 
as gas, can be turned into solid ice. 

Oxygen gas can be separated from some of the substances with 
which it is united, and so can be obtained alone by itself. The 
chemist commonly uses for this purpose a certain powder. What 
this powder is I will not tell you now, but shall notice its compo- 

B 



18 



OXYGEN. 



How oxygen is obtained separate from other substances. 



sition in another part of this book, when you can understand it 
better than you can at present. This powder is heated in a glass 



Fig. 3. 



vessel, called a re- 
tort, by a spirit 
lamp placed un- 
derneath, as rep- 
resented in Fig. 3. 
The oxygen, sep- 
arated from the 
J powder by the 
heat, passes over 
through the neck 
of the retort, and 
bubbles up from 
the beak, as it is 
called, which you 
see dips under the water in the large tin vessel. There is over 
the beak a glass vessel, a common candy -jar, with its open end 
down. This jar is full of water at first, the water being kept in 
it by the pressure of the air on the surface of the water around 
it, as explained in the Child's Book of Nature, Part III., Chap- 
ter IV. As the beak of the retort is put under the mouth of the 
jar, the gas goes up, as you see, in bubbles through the water, 
because it is lighter than water, and takes its place in the upper 
part of the jar. In this way the jar may be filled with the ox- 
ygen gas. In collecting this gas, the first bubbles must be al- 
lowed to escape, and not be caught in the jar, for there is of 
course air in the retort above the powder, and this is driven out 




OXYGEN. 19 



Pneumatic trough. Simple contrivances. 

by the gas as it rises. You do not want to catch the air. You 
let that go, and catch the gas that comes out after it. 

In the large vessel, which is called the pneumatic trough, there 
is always a shelf on one side, a little under the surface of the wa- 
ter. The jars stand on this shelf. They are filled by having the 
beak of the retort near the edge of the shelf, and bringing the jar 
to be filled over the beak. Or there may be an opening in the 
shelf, through which the beak may discharge the gas into the jar 
over it. In this way you can fill quite a number of jars with the 
gas, and have them stand on the shelf ready for use. You see a 
pipe on the side of the trough. This is to keep the water from 
rising too high, as it is forced down from the jars by the gas go- 
ing up into them. 

It is vejy easy to take a jar of gas out from the trough when 
you want to use it for experiments. Your own ingenuity may 
contrive several ways. One is to slip a plate or a piece of win- 
dow-glass under the mouth of the jar as you remove it. 

In Fig. 4 you see a more simple apparatus for getting oxygen 
Fig> 4> gas. At a is a glass flask, with a cork in its 

I/^X^ mouth. Into this cork is fitted the tube 5, 

A \ fil which lets the gas pass into the jar c. The 
- "g? \ jjjg small trough, you see, has a shelf. You can 
m .^^dH^M ma ^ e a pneumatic trough of almost any 
z&y 1 W thing that will hold water, contriving a shelf 

of some kind. Indeed, you can make the whole apparatus even 
more simple than is represented here.* 

* Assistance will, of course, be rendered by the teacher to pupils that may wish 
to try experiments, in arranging apparatus. A little ingenuity can make very com- 



20 



OXYGEN. 



Burning various substances in oxygen. 



There are many beautiful experiments that can be tried with 
oxygen. I will notice some of them. 

Put a lighted candle into a jar of oxygen, as in Fig. 5. It will 
Fig. 5. burn now with a dazzling brightness, and will be rapidly 
consumed. The reason is this. It is the oxygen in the 
air that makes the candle burn at all. Of course, the 
more oxygen gets to the candle, the brighter will it burn. 
Now only about one fifth of the air is oxygen, and so the 
candle will burn five times as fast and as brightly as in 
common air. 

For the same reason, if a lighted piece of char- 
coal, which, you know, in the air is only of a dull 
red color for a little while, and then goes out, be 
placed in a jar of oxygen, it will burn very actively, 
and throw off sparks all around, as Fig. i. 

represented in Fig. 6. 




Fig. 6. 






There is no substance that makes so brilliant 
a light on burning in oxygen as phos- 
phorus, Figure 7. A very thick white 
smoke arises, which is most brilliantly 
illuminated. 

If sulphur be burned in oxygen gas, the smoke 
has a most beautiful blue color; and the smoke is 
arranged in a very singular way, as seen in Fig. 8. 

mon household things available. Professoi Porter has very prettily shown this in 
his Chemistry — a phial, a test tube, a bowl, some tobacco-pipes, and a spirit lamp be- 
ing all that is necessary in some cases. Glass tubes are often very convenient. 
These can be bent readily into any required shape by heating over a spirit lamp. 
Holes can be made through corks with a round file, so that the tubes can be passed 
through them. 



OXYGEN. 21 



Burning of iron in oxygen. 




It goes up straight in the middle of the jar, and then falls in cu- 
rious rings down the sides. 

There are some substances which most people think can not 
burn at all, that will burn very readily in oxj^gen. Iron is one 
of these. If you take a piece of steel wire, and twist it 
as you see in Fig. 9, you can make a splendid fire with 
it in the oxygen. But how will you manage it? You 
can not set it on fire in the air, and then introduce it into 
the oxygen, as is done with the phosphorus, charcoal, etc. 
It is managed in this way. The end of it is dipped in 
sulphur, or has a bit of something which will burn in 
common air fastened to it, as cotton or charcoal. You light this 
substance, and then introduce the wire into the jar of oxygen. 
The substance on the end of the wire, in burning, sets fire to the 
wire itself, and now the sparks fly most merrily. 

Questions. -*What is said about the word oxygen? How do you have a great 
deal to do with oxygen ? What would happen to you if you could not get any of it 
into your lungs ? What is said about oxygen as food ? Give the comparison be- 
tween stomach-food and lung-food. What does oxygen gas help to make in your 
body ? What is flame ? Of what is the gas made in a candle or lamp ? What is 
said about gases being transparent ? What does the word transparent come from ? 
Mention some of the things in which there is oxygen. What is said about its mak- 
ing a part of solid substances ? Tell about obtaining oxygen gas. Describe the 
pneumatic trough, and the way in which it is used in collecting gas in jars. De- 
scribe the apparatus represented in Fig. 5. Describe and explain the experiment 
with a lighted candle. Give the experiment with charcoal. How does phosphorus 
burn in oxygen ? Describe the experiment with sulphur. Describe the experiment 
with iron. 



22 NITROGEN. 



How nitrogen differs from oxygen. Why nothing can burn in nitrogen. 



CHAPTEE in. 

NITROGEN. 

To every gallon of oxygen in the air there are about four gal- 
lons of another gas called nitrogen. 

This gas is very different, in some respects, from oxygen. 
Nothing will burn in it. Suppose that you have two jars, in 
one of which is oxygen, and in the other nitrogen. If you put a 
lighted candle into the jar of oxygen, it will, you know, burn 
brighter than it does in the air. But if you take it out of the 
oxygen, and put it into the jar of nitrogen, it will go out. Not 
even phosphorus will burn in nitrogen. So, if all the oxygen 
should be taken out of the air, every fire and light would go out. 

Besides this, no animal can live in nitrogen gas. If you put a 
mouse into a jar of oxygen he will be more lively than in com- 
mon air, and will act as if he were crazy, jumping about in the 
most singular manner; but if you should put him into a jar of 
nitrogen, he would die at once. And if all the oxygen should be 
taken out of the air, all animals would die, just as all the fires and 
lights would be extinguished. 

But this nitrogen gas does not really put out fires and lights. 
A light, when pla^d in a jar of nitrogen, goes out merely because 
there is no oxygSp It must have oxygen to keep on burning. 
Only put a little oxygen in with the nitrogen, and the candle will 
burn ; for it does burn well in a mixture of oxygen and nitrogen, 



NITROGEN. 23 



Why animals can not live in nitrogen. What would happen if the air were all oxygen. 

that is, common air, in ^hich there is four times as much nitrogen 
as oxygen. 

So, too, nitrogen does not kill any animal, although he can not 
live in it. It does not act as a poison when it goes into the 
lungs ; for there is going into the lungs of all animals, all the 
time, four times as much nitrogen as oxygen. The mouse dies 
in the jar of nitrogen simply because nitrogen can not keep him 
alive, as oxygen does. 

Of what use, then, is the nitrogen in the air, as it does not help 
to make any thing burn, or keep any thing alive? I will tell 
you. 

Suppose that the air were all oxygen instead of being a mix- 
ture of oxygen and nitrogen. What would happen ? You can 
see by calling to mind the experiments in which different things 
were burned in jars of oxygen. Our fires and lights would burn 
very brightly. This would sometimes be quite convenient. We 
should not be troubled with dull fires and dim lights. It would 
be one of the easiest things in the world to kindle up a fire. But 
then, on the other hand, there would be a great deal of incon- 
venience and danger from so much oxygen. Things would burn 
too fast. They would be too ready to take fire. We should have 
things taking fire much oftener than now ; and when a fire once 
was a going, it would be very hard to put it out. If a block of 
houses should take fire at one end, there would be no stopping 
the fire ; it would go through the whole block. Whole towns 
and cities would be often burned up. The sparks from locomo- 
tives would be continually setting fire to some bridge, or fence, or 
house. We should have to be much more careful about fire than 



24 NITEOGEN. 



Why there is so much nitrogen in the air. 



we now are, and it would be one of the chief occupations of life to 
put out fires. 

Besides all this, if the air were wholly oxygen it would be in- 
jurious to all animals. It would be too heating, too stimulating. 
With so much oxygen going into our lungs, we should be all the 
time as hot as we are after exercising violently. This would 
make us very uncomfortable. "We should be forever fanning 
ourselves, and drinking cold water, and seeking for cold air. In- 
flammations and fevers would be produced, and we could not live 
long in this way. 

It is chiefly for these reasons that God has given us our oxy- 
gen mingled with so much nitrogen. It is very much as we take 
some medicines. They are put into sugared water because it 
would not do for us to take them clear. The sugared water is to 
the medicine as the nitrogen is to the oxygen. Suppose the med- 
icine is some strong acid. It would make your mouth sore if you 
should take it clear, so we dilute it, as we say, with sugared wa- 
ter. In like manner, the oxygen is diluted with nitrogen, that we 
may take it into the lungs without harm. 

Nitrogen, you see, is a very mild sort of thing. It just goes 
along every where with the smart and lively oxygen, and keeps it 
from doing too much in the ways that I have mentioned. But 
you will find, before you get through with this book, that nitrogen 
is, after all, no milk-and-water character. It is ready to do when 
there is need of its doing, and it unites with many substances to 
do some very smart things. I will mention here only two exam- 
ples of this. Nitrogen unites with oxygen, as you will see in the 
next chapter, to form one of the most powerful acids in the world, 



NITROGEN. 25 



An experiment and its explanation. 



aqua fortis. It is also one of the two ingredients of ammonia, or 
hartshorn, which so tingles your nose whenever you smell it. 

You can get nitrogen gas from the air by a very pretty exper- 
iment. All that you need is a large basin, a good-sized glass jar, 
a flat cork smaller than the open end of the jar, some powdered 
chalk, and a bit of phosphorus. Fill the basin with water ; hol- 
low out a little place on the cork and sprinkle some chalk into it; 
place the phosphorus on the chalk, and then put the cork into the 
water. Setting fire to the phosphorus, you put the jar over it 
with its edge in the water. Think, now, what you have in the 
jar. There is a mixture of oxygen and nitrogen, that is, air. 
Then you have the burning phosphorus. Now the phosphorus 
burns because there is oxygen there. If there were nothing but 
nitrogen in the jar it would not burn at all. If you watch the 
experiment you will soon see that the phosphorus burns rather 
dimly, and at length goes out, although there may be considera- 
ble phosphorus left on the chalk. Why is this? It is because 
the oxygen is all gone, and there is nothing now but nitrogen in 
the jar. 

You will see that the cork has risen in the jar, being pressed 
up by the water. Why? The part of the air in the jar which 
is oxygen is used up, and so makes room in the jar, and the wa- 
ter and cork are pressed up to fill this room. One fifth of the air 
in Wm jar is gone, for oxygen makes one fifth of the air. There 
is, then, this amount of room made in the jar. 

But what has become of the oxygen ? It is not lost in the 
burning. It is united with the phosphorus, and they, together, 
make the white smoke which arises when phosphorus is burned 



26 NITROGEN. 



Phosphoric acid. Affinity of phosphorus for oxygen. 

in oxygen, as represented in Fig. 7. This smoke is an acid, which 
the oxygen and the phosphorus make together, called phosphoric 
acid. This soon disappears, and the reason is that the acid likes 
the water so much that it just goes down and unites with it. This 
leaves the nitrogen alone in the jar. 

In this experiment the nitrogen is let alone. The burning phos- 
phorus will have nothing to do with it, but takes all the oxygen 
out of its company. The phosphorus likes the oxygen, and is 
ready to join company with it; or, as the chemists say, it has an 
affinity for oxygen, while it has not for nitrogen. 

You will want to know how much phosphorus to use. If your 
jar will hold a quart, a piece of phosphorus twice the size of a 
large pea will be needed. As phosphorus takes fire easily, great 
caution is required in managing it. 

Questions. — "What proportion of air is nitrogen ? Tell about putting a lighted 
candle in this gas. What would happen to the fires and lights if all the oxygen 
were taken out of the air ? Tell about the difference between oxygen and nitrogen 
in regard to life. Why does a light go out when put into nitrogen gas ? Why does 
an animal die when put into it ? Tell what would happen to fires and lights if the 
air were all oxygen. What influence would it have on animals ? Of what use is 
the nitrogen in the air? Give the comparison of the medicine in sugared water. 
What does the word dilute mean? What is said about the character of nitrogen? 
What two very active substances are partly composed of it ? Tell how you would 
arrange your apparatus for obtaining nitrogen. What now is the jar filled with ? 
Why does the phosphorus burn? Why does the cork rise in the jar? Whit be- 
comes of the oxygen in the jar ? How is it that the nitrogen is left alone in the jar ? 



AQUA FORTIS AND THE LAUGHING GAS. 27 

Nitric acid a compound. How lightning makes it in the air. 



CHAPTER IV. 

AQUA FORTIS AND THE LAUGHING GAS. 

In air, as you have seen, oxygen and nitrogen are only mixed 
together. The oxygen is diffused through the nitrogen as alco- 
hol is diffused through water when they are mixed. But oxy- 
gen and nitrogen can be united together in such a way as to form 
compounds that are very different from the mixture that we call 
air. 

One of these compounds is nitric acid. This is called aqua 
fortis, which is the Latin for strong water, because it is so very 
powerful an acid. It will eat cloth, and even flesh, if dropped 
upon it. How strange it is that such a biting acid is composed 
of two gases that are so quietly going into our lungs every time 
that we breathe ! 

These gases, mixed together so thoroughly in the air, have no 
disposition to unite together to form this acid. It is very difficult 
to make them unite. All the shaking which the air gets in vi- 
olent winds and whirlwinds will not do it. Air is sometimes 
greatly heated, but the heat of the hottest furnace can not unite 
the oxygen and the nitrogen of the air in the furnace together. 
A flash of lightning, as it passes along through the air, will make 
them unite so as to form nitric acid ; but there is only a little of 
it made in this way. This little, however, being carried down in 
the rain, is of use to the farmer and the gardener in making things 



28 AQUA FOETIS AND THE LAUGHING . GAS. 

Singular effects of the laughing gas. How it differs from nitric acid. 

grow. How this is you will learn, when you are a little older, in 
the next book that I will give you on Chemistry. 

There is another compound of these two gases which is of a 
very different character from the nitric acid. It is in the form 
of a gas. It can be breathed, and it does not irritate the lungs. 
It produces, however, a very singular effect upon the system, 
making the person who breathes it delirious. In this delirium 
persons act very differently from each other. One, perhaps, bows 
and smiles continually ; another dances ; another tries to kiss all 
the ladies present ; another laughs ; another declaims with, great 
eloquence; another wants to fight — and so on. The delirium 
lasts, at farthest, but a minute or two commonly ; and when the 
person comes to himself he does so all at once, and seems to be 
half ashamed of what he has been doing. 

Now a person in breathing this gas takes into his lungs oxy- 
gen and nitrogen as he does when breathing air ; but they are 
not merely mixed, as they are in air, but are a compound. They 
make a new thing, different from both the oxygen and nitrogen, 
as they do when they unite to form nitric acid. Neither nitrogen 
or oxygen, or their mixture in air, ever produces an intoxicating 
delirium, as does their compound, the laughing gas. 

Observe how these two compounds, nitric acid and the laugh- 
ing gas, differ from each other. One is a liquid which stains and 
corrodes. The other is a gas, soft and mild, but when breathed 
it makes people crazy. It is so generally disposed to make them 
pleasant and laughing that this has given it its name. 

The reason of the difference between the two is in the different 
proportions of the ingredients. The nitric acid has a great deal 



AQUA FORTIS AND THE LAUGHING GAS. 29 

What would happen if oxygen and nitrogen united easily. 

more of oxygen in it than the laughing gas has. It has just five 
times as much ; that is, to every pound of nitrogen there is five 
times as much oxygen in nitric acid as there is in the laughing 
gas. 

There are three other compounds of oxygen and nitrogen, mak- 
ing five in all. The proportions of oxygen in them are exactly 
as 1, 2, 3, 4, and 5. The laughing gas has the smallest propor- 
tion, 1, and the nitric acid the highest, 5. 

Suppose that the oxygen and nitrogen in the air were very 
much disposed to unite together, forming compounds. What 
would happen ? Suppose, for example, that once in a while these 
gases should unite in the air and make a large quantity of laugh- 
ing gas. In whatever country this should happen, all the people, 
men, women, and children, would be running about crazy, laugh- 
ing, kissing, and playing all manner of strange pranks. 

Or suppose that these gases should all at once unite to form 
nitric acid in the air. It would rain down upon the people, de- 
stroying the life of every animal and every plant, eating them, 
and thus make the earth desolate. 

If the nitrogen and oxygen that are now in your lungs should 
in a moment unite to form nitric acid, it would so irritate and 
corrode them that you would probably die instantly of suffocation. 

But the Creator has so made these gases that they can not 
unite together when they are mixed, and the air is one of the 
mildest and pleasantest of all the mixtures that he has given us. 
When, at the end of the creation, he pronounced all his works to 
be " very good," he meant the air as well as other things. It is 
good — very good — for all the purposes for which it is wanted. 



30 AQUA FORTIS AND THE LAUGHING GAS. 

Contrast between phosphorus and nitrogen in uniting with oxygen. 

God has made some things in such a way that they will unite 
together very readily. Thus you saw, in the experiments in 
which phosphorus was burned, on pages 20 and 25, that phos- 
phorus unites with oxygen and forms phosphoric acid. Now, if 
phosphorus were diffused through the air in fine particles as ni- 
trogen is, it would not do to have it unite so easily with oxygen. 
But there is none of it in the air, and it is present only in those 
places where it will not do harm, but good, to have it like the ox- 
ygen so well. This, and many other things that I shall tell you 
about, show that the Creator fits every thing exactly for the 
places it is to be in, the company that it is to keep, and the things 
that it is to do. 

Questions. — Is air a compound ? Give the comparison about alcohol and water. 
Of what is nitric acid composed? Why is it called aquafortis? What is said of 
the difference between this and the gases that compose it ? What of the difficulty 
of making these gases unite to form nitric acid ? Tell about the effect of lightning 
upon them. Of what is the laughing gas composed ? What are its effects when 
breathed ? Why is it called laughing gas ? What is said of its being a compound ? 
What of the difference between this compound and nitric acid ? What is the cause 
of this difference ? How many compounds of oxygen and nitrogen are there ? What 
are the proportions of oxygen in them ? If the oxygen and nitrogen in the air were 
very ready to unite together, what effects would be produced ? What would happen 
if the oxygen and nitrogen now in your lungs should all at once unite to form nitric 
acid ? What is said about the creation of air ? What about the readiness of phos- 
phorus and oxygen to unite ? 



CARBON. 31 



Carbonic acid in the air. Difference between elements and compounds. 



CHAPTER V. 

CARBON. 

Thus far I have spoken of there being two gases in the mix- 
ture that we call air. But there is a third gas, in very small 
quantity, in the air, called carbonic acid, or carbonic acid gas. 
There is only one gallon of this gas in every 2500 gallons of air. 
Fi? 10 . The proportions of the three gases in the 

air may be illustrated by Fig. 10. The 
largest square represents the nitrogen, 
the next the oxygen, and the very little 
one the carbonic acid. Although there 
is so small a proportion of this gas in the 
-& air, the little that there is has a very im- 
portant influence, as you will soon see. 

Carbonic acid gas differs from oxygen and nitrogen in being 
composed of two things. Oxygen is one thing, and so is nitro- 
gen. Neither of them can be in any way divided into two things. 
They are therefore called elements, or elementary substances. But 
carbonic acid is not an element, but a compound, for it is made of 
two things united together in one. Observe that these two things 
are not mixed together as the two elements nitrogen and oxygen 
are in the air, but they are united together so as to make one thing 
in effect — as much one as if it were really an element. The two 
elements which compose carbonic acid are your lively friend that 



32 CARBON. 



Charcoal. Coal. Black lead. Diamonds. 

you have become so well acquainted with, oxygen, and another 
that I will now introduce to your acquaintance, carbon. 

Carbon appears in various forms, but the most common is that 
of charcoal. It is for this reason that the two names, charcoal 
and carbon, are ordinarily used by chemists as meaning the same 
thing. The various kinds of coal that we burn are mostly car- 
bon. Plumbago, or black lead, as it is called, is a form of carbon. 
It is this which is used in our lead-pencils. The name black lead 
is very improper, for there is not a particle of lead in this sub- 
stance. It is wholly carbon, with the exception of a very, very 
little iron which is generally present in it. 

In the diamond we have carbon perfectly pure and beautifully 
crystallized. How strange that this most costly and brilliant of 
gems should be made of the same material with common dull and 
black charcoal ! But so it is. And yet no man has ever discov- 
ered any way of changing charcoal into diamonds. The Creator 
alone knows how diamonds are made. 

Diamonds are very expensive. Fifty dollars will buy but a 
small one. The largest one ever found is about the size of half a 
hen's egg. The famous one which now belongs to the Queen of 
England is less than half of the size of this, but it is valued at 
three millions of dollars. 

Diamonds are commonly found in the sands of rivers, and there 
is generally gold with them. There are many diamonds found 
in Brazil. A few have been feund in this country, mostly in 
North Carolina. 

The diamond is the hardest substance in the world. You can 
not scratch a diamond with any thing else but another diamond ; 



CARBON. 33 



Burning of diamonds. How charcoal is made. 

and in preparing a diamond to be set, it is ground with the pow- 
der of diamonds. The instrument with which the glazier cuts 
glass has a small diamond in its end. 

All the different forms of carbon can be burned. Most of them 
burn in common air ; but black lead and the diamond will not. 
To burn them you must have oxygen alone, without any ni- 
trogen. 

Observe what comes from this burning of carbon. You re- 
member that in Chapter III. I told yo.u that when phosphorus 
is burned it unites with the oxygen of the air, making phosphoric 
?,cid, which goes up in fumes. So, when carbon burns, it unites 
with oxygen, and forms carbonic acid gas. This gas is formed 
when we burn a diamond in oxygen, as well as when we burn 
common charcoal. Tt is rather an expensive experiment to burn 
up a diamond, and it has not often been performed. 

The charcoal that we use is, you know, made from wood. It 
is wood that is only partly burned. It is made by burning wood 
in a heap, which is covered up with turf and dirt. There are 
some small openings left above and below, so that a little air 
can circulate among the wood, and thus keep up a smothered 
burning. 

The explanation is this. "Wood is composed of carbon, united 
with some other things. Now what we want to do is to get the 
carbon alone by itself. This we do by burning the wood just 
enough to drive these other substances that are with the carbon 
in the wood off into the air. Some of the carbon is lost in this 
burning, for the oxygen unites with it, and they fly off together 
as carbonic acid gas. But most of the carbon remains, and we 

C 



34 CABBON. 



Experiment. How hard coal was made. Smoke and soot. 

have it in the shape of charcoal. In making charcoal it is neces- 
sary to take great care not to let in too much air, lest the fire 
should be too free, and burn out more of the carbon than is re- 
quired. As there is always considerable water even in wood 
that seems to be very dry, this is driven off by the heat 
mingled with the smoke. 

You can readily make charcoal in a small way. Take a 
test tube, a, Fig. 11, and hold a burning slip of wood, 5, in 
it. The tube prevents the air from getting freely to the 
wood, and makes a smothered burning, and so you have a 
slender piece of charcoal. 

Hard coal is almost wholly carbon. It differs from char- 
coal in being very solid. It is supposed that all the coal 
that man gets out of coal-mines was once wood. How, then, did 
it become coal ? Man can not make such coal from wood ; but 
Grod can do a great many things that man can not. But do we 
know how the Creator made this hard coal? We know some- 
thing about it. We know that there must have been great heat 
and great pressure at the same time. While the wood was heated 
or partly burned, the rocks, we know not how high, were press- 
ing down upon it, and so made the coal very solid. 

Soot is mostly carbon. It forms in the chimney in this way. 
Most of the wood, in burning, has its carbon unite with the oxy- 
gen of the air, forming carbonic acid gas, which flies off. This 
gas you can not see any more than you can air. But the smoke 
of the fire you can see, so that there must be something in it be- 
sides carbonic acid. What you see is made up mostly of very 
fine particles of carbon which are thrown off from the burning 



CARBON. 35 



What lamp smoke ig. How lampblack is made. 

wood and fly up the chimney. Many of these particles lodge on 
the chimney's sides in the form of soot. 

When a lamp smokes because the wick is too high, the smoke 
is made up of these little particles of carbon, for there is carbon 
in oil as well as in wood. The reason that it smokes is that 
more carbon comes up the wick than is sufficient to unite with 
the oxygen that comes to it. If you could make the oxygen 
come to the wick faster, it would stop the smoking ; for then 
there would be oxygen enough to turn all the carbon into car- 
bonic acid gas. So, too, the smoking would stop if you should 
put the lamp into a jar of oxygen gas. There would, in that case, 
be five times as much oxygen all around the wick as there is 
when the lamp is in the air. 

The lampblack so much used in painting is a kind of charcoal. 
It is made by letting the smoke of burning pitch or rosin into a 
Fig. 12, sort of chamber lined with leather. In Fig. 

12 you see the process represented. In the 
iron pot, a, some pitch or tar is made to boil, 
and the fumes pass into the chamber &, c, 
which is lined with leather. At d is a sort 
of hood, the height of which can be regu- 
lated by a pulley. This is to keep the 
fumes from passing upward too rapidly. 
The lampblack collects on the leathern 
sides of the chamber. 

There is much carbon in many very dif- 
ferent things that we see every where. There is carbon in chalk 
and marble. It is combined in these with oxygen and lime, so 




36 CARBON. 



Carbon very abundant, and in many different substances. 



that it does not show itself as carbon any more than it does in 
carbonic acid gas. It is in egg-shells, oyster-shells, and in all 
shells. It is in all wood, as I have before told you, and makes 
an important part of all leaves, flowers, and fruit, and, indeed, of 
most vegetable substances. Your body, and the bodies of all an- 
imals, have carbon as one of its principal ingredients. But it 
does not show itself in them as carbon any more than it does in 
the white chalk and marble. It is hidden in them by being 
united with other things. By separating it from these things, it 
can be brought out from its concealment, and be shown as car- 
bon, as you have seen that we do when we make charcoal from 
wood. 

Questions. — How many gases are there in the air ? How much carbonic acid gas 
is there in it ? Explain Fig. 10. What is an element ? What elements are there 
in the air ? Why is carbonic acid called a compound ? What are the two elements in 
it ? What is the most common form of carbon ? What is plumbago ? What is the 
diamond ? What is said of the making of diamonds ? What of their size and ex- 
pense ? Where are they found ? What is said of their hardness ? What is said 
of burning carbon ? What is formed when we burn it ? How is charcoal common- 
ly made ? What is the explanation ? What care is needed in making charcoal ? 
What becomes of the water that is in the wood ? Explain Fig. 11. How does hard 
coal differ from charcoal ? How is it probable that it was made ? Tell about soot. 
Why does a lamp smoke when the wick is high ? Why would it stop smoking if you 
should put it into oxygen gas ? What is lampblack, and how is it made ? Mention 
some of the substances that have carbon in them. What is said about separating it 
from them? 



CARBONIC ACID. 37 



How carbonic acid is obtained from chalk and marble. 



CHAPTER VI. 

CARBONIC ACID. 

Carbonic acid gas, as you learned in the previous chapter, is 
composed of the solid carbon and the gas oxygen. The solid is no 
longer a solid, but is united with a gas to form a gas ; and then 
this gas thus formed is united with many substances to form 
solids. For example, in chalk and marble we have this gas com- 
bined with lime. 

Now we can obtain carbonic acid from either of these sub- 
stances, chalk and marble, by putting with it something which 
will take away the lime from it. An acid which we call muriatic 
acid will do this, because it has a greater liking or affinity for the 
lime than the carbonic acid has. If we pour, then, some of this 
acid into a glass vessel, and drop in some pieces of chalk or mar- 
ble, we can get the carbonic acid gas away from the lime. An 
effervescence at once occurs. This is caused by the gas, which 
is set free from the chalk as the muriatic acid takes the lime away 
from it. The gas rises, and, pushing up the air before it, fills the 
glass vessel. 

You will want to know how much of the muriatic acid and the 
chalk you will need to use in making the gas. If your glass jar 
holds a quart, pour into it two teaspoonsful of the acid. Then 
drop into it little bits of chalk till the effervescence ceases. In 
this way you will get your jar full of the gas, the muriatic acid 
and the lime being united together in the bottom of it. 



38 CARBONIC ACID. 



Various ways in which we make this gas every day. 



This is commonly spoken of as one of the ways of making this 
gas; but this is hardly a proper expression. The gas is not 
made ; it is in the chalk, united with the lime, and we only sepa- 
rate it from the lime by putting muriatic acid there to take the 
lime away from it. 

But there are ways of making this gas. For example, when we 
burn charcoal in a jar of oxygen, as represented in Fig. 6, the 
carbon unites with the oxygen in the burning, and we have in 
the jar carbonic acid gas. Here we make the gas, for we cause 
the carbon to unite with the oxygen and thus form it. 

So, also, we make carbonic acid if we burn charcoal in a jar of 
common air. In such case, however, we do not get it alone, but 
it has a large quantity of nitrogen mingled with it ; you can tell 
how much, for you know what the proportion of nitrogen is in air. 

Whenever, in fact, you. set fire to any common thing in the air, 
wood, or a candle, or a bit of rag or paper, you set a going the 
manufacture of carbonic acid gas. There is carbon in all these 
things, and in the burning it unites with the oxygen of the air, 
and forms carbonic acid. 

For most of the experiments that we want to try with carbonic 

acid, it answers to obtain it in the way that I first mentioned ; 

but for some experiments it will not do to have any thing left in 

Fig. i3. the bottom of the jar. In that case the gas must be 

made in a retort or a flask, and so pass out and be 

collected in jars, as you remember we obtain oxygen 

gas. Or, we can obtain it in the way represented in 

Fig. 13. Here you see a flask containing the chalk 

and the muriatic acid. A bent tube is fastened into the cork at 




CARBONIC ACID. 39 



Nothing can burn in this gas. No animal can live in it. 

one end, and the other end is at the bottom of the jar in which 
we want to collect the gas. Now observe the operation. There 
is air in both the flask and the jar. This is driven out by the 
gas as it forms. This gas is considerably heavier than air, and so 
the air in the jar very readily passes out, and leaves the jar full 
of the gas. 

Let us look, now, at some of the qualities of carbonic acid gas. 
It has no color, and is transparent. In these respects it is like ox- 
ygen and nitrogen. It has a faint smell and a slightly acid taste. 

Nothing will burn in this gas. If you lower a candle into a 
jar of it, it will go out. A very pretty experiment is sometimes 
tried, showing how different this gas is from oxygen in this re- 
spect. We have two jars, one full of oxygen, sind the other of 
carbonic acid. If the candle be lowered into the jar of carbonic 
acid, it goes out. If, now, we instantly put it into the jar of oxy- 
gen, the spark of fire on the wick lights up at once into a bright 
flame. And so we can pass the candle back and forth several 
times, putting it out and relighting it each time. 

Why does the candle go out in the carbonic acid? Because 
there is no oxygen there to make it burn. But perhaps you will 
say that there is oxygen there, for carbonic acid is composed of 
oxygen and carbon. True ; but the oxygen is not there as oxy- 
gen, for it is united with the carbon so as to make something en- 
tirely different. The union is a close one. The carbon clings, as 
we may say, to the oxygen, and will not let it go to the burning 
candle. 

As nothing can burn in this gas, so no animal can live in it. 
Put a mouse into a jar of it, and he will die at once. I have told 



40 



CARBONIC ACID. 



Pouring carbonic acid upon a candle. 



Weighing this gas. 



Fig. 14. 



you that there is a little of this gas in common air, but it is so 
very little that it does no harm to us and to other animals. 

Carbonic acid gas is much heavier than air. You can therefore 
pour it, like water, from one vessel into another. Of course the 
vessel into which you pour it is full of air. 
What becomes, then, of the air ? It rises and 
goes out of the vessel, just as oil would if 
you should pour water into a vessel filled 
with it. 

Suppose, as represented in Fig. 14, you 
have a lighted taper in a jar of common air, 
and hold a jar of carbonic acid gas over it, 
as you see there ; the gas will go down into 
the lower jar, forcing up the air, and put out 
the light. 

In Fig. 15 is represented a very pretty ex- 
periment, which shows that this gas is heav- 
ier than air. In the 
first place, you balance 
a jar by a weight. I 
say balance a jar. Is 
that exactly correct ? 
Is there not something 
in the jar? "No," you 
will perhaps say, " it is 
empty." But think a 




Fig. 15. 




moment. That jar is full of something, and that something has 
weight. It is full of air. You have balanced, then, a jar full 



CAEBOHIC ACID. 



41 



Drawing up gas with a bucket. 



Soap-bubble floating on gas. 



of air. Now if, as represented, some carbonic acid gas be poured 
down into the jar on the scales, the jar will fall and the weight 



Fig. 16. 



will rise. Why ? Because there is now a gas 
in the jar that is heavier than air. 

If you have a jar filled with this gas, you 
can take it out with a little bucket, as seen in 
Fig. 16. As you take one bucketful after an- 
other out, you can pour it away as you would 
water; and the air will go into the jar to take 
the place of the gas as fast as you remove it. 

If you blow a soap-bubble and let it fall into 
a jar full of carbonic acid gas, it will not go to 
the bottom of the jar and break, as it would if 
the jar were full of air. It will fall down a lit- 
tle into the jar, and then go back and remain in 
its open mouth. "Why is this? The air that 
you have blown into the bubble is lighter than the gas in the jar, 
and the bubble therefore floats on the surface of the gas as a boat 
floats on the surface of water. If the jar be only half full of the 
gas, air filling, therefore, the upper half, the bubble will stop half 
way down in the jar, and there remain. 

Questions. — What is said of the formation of carbonic acid gas? What is the 
composition of chalk and marble ? How can we get the carbonic acid from them ? 
If you wish to make a quart of carbonic acid gas, how would you do it ? Explain 
Fig. 13. How is carbonic acid like oxygen and nitrogen ? What are its taste and 
smell ? Give the experiment with the two jars of gases. Why does the candle go 
out in the carbonic acid ? What is said of the union of oxygen with carbon in this 
gas? How about living in carbonic acid? What is. said of the weight of this gas ? 
Explain Fig. 14. Give the experiment represented in Fig. 16. Describe and ex- 
plain the experiment with the soap-bubble. 




42 



CARBONIC ACID. 



An amusing experiment. 



Putting out a fire in a coal-mine. 



CHAPTER YIL 

carbonic acid — Continued. 



Fig. IT. 



A very entertaining experiment, showing that carbonic acid 

gas is heavier than air, 
is represented in Fig. 17. 
The gas is poured down 
upon a row of lighted 
candles, putting out one 
after another. 

This gas has been used 
to put out fire. Some 
years ago a fire began in 
a coal-mine in Scotland, 
and burned away at such 
a rate that it could not be 
put out by any common means, and the mine could no longer be 
worked. There was danger that a large amount of coal would be 
consumed if the fire continued long. A Mr. Gurney contrived in 
some way to make a great quantity of carbonic acid gas in a part 
of the mine where it would sink down to the fire, and put it out. 
As carbonic acid gas is so heavy, it is apt to remain below air 
wherever it collects. It sometimes is produced in considerable 
quantity in wells. When this is the case it remains at the bot- 
tom of the well. Suppose a man goes down into such a well to 
clean it ; he will have no difficulty at first, because the air is 




CARBONIC ACID. 



43 



Carbonic acid gas in wells. 



Expedients for getting rid of it. 



good ; that is, it has enough of oxygen in it, and not too much of 
carbonic acid. But when he gets near the bottom, where the 
carbonic acid gas has accumulated, he gasps for breath, and falls. 
Perhaps some one, not understanding the cause of the trouble, 
goes down to relieve the man, and he also falls senseless. Many 
lives have been lost in this way. 

Now how can we find out whether this gas has collected in a 
well ? Let a light down. If it goes out, there is a good deal of 
the gas there ; and if it burns dimly when it comes near the bot- 
tom, there is enough of the gas to make it dangerous. A very 
good way is for the man who goes down a well to take a candle 
Fig. is. with him, as you see in Fig. 18. 

He must hold the candle con- 
siderably below his mouth, or it 
will do no good. If his light 
■- goes out, or becomes quite dim, 
he must stop at once, for anoth- 
er step would bring his mouth 
down into the gas, so that he 
would take it into his lungs. 

Now the question comes, 
when there is some of this gas 
in a well or pit, how can we get 
rid of it, so that it may be safe 
for a man to go down into the 
well ? There are several expe- 
dients for this. One is to let 
down a bucket a good many times, turning it each time upside 




44 



CARBONIC ACID. 



Burning straw in a well. 



Throwing down slaked lime. 



down in the air to let the gas fall out. This will remind you of 
the experiment represented in Fig. 16. 

But this will not get all the gas out. "Well, another expedient 
is to let down a bundle of straw or shavings on fire. This heats 
the gas, and so makes it lighter ; and, therefore, if the bundle be 
held to one side of the well, the heated gas will pass up that side, 



Fig. 19. 



while cool good air will go down the other to 
take its place. The manner in which this op- 
erates can be illustrated by the experiment in 
Fig. 19. In a jar of carbonic acid gas there is 
placed a flask full of hot water, and corked. It 
rests on a pad, to keep it in its place at the 
side of the jar. This heats the gas all around it, 
and there is, therefore, an upward current on that 
side of the jar, while there is a downward cur- 
rent of cool good air at the other side. The two 
currents are indicated by the arrows. That the 
gas is driven out can be shown by letting a light- 
ed taper down into the jar. If it is all gone the 
taper will burn as brightly as when it is outside. 
Another expedient is to throw some slaked lime, mixed with 
water, down the sides of the well. Observe how this operates. 
You remember that chalk is composed of carbonic acid and lime. 
Now there is the carbonic acid in the well, and if you put the 
lime there, so that this gas can get at it, they will unite together 
and form chalk. This is the object of having the mixture of lime 
and water drip down the sides of the well. The gas unites with 
the lime, and so chalk is formed, and sticks to the stones. You 




CARBONIC ACID. 45 



Carbonic acid in the air. Mingling of gases. 

can see that if the dry lime were thrown down it would pass 
quickly through the gas, and be lodged in the water below where 
the gas could not get at it. 

There is always, as I have before told you, some carbonic acid 
gas in the air, but it is mixed up with the nitrogen and oxygen. 
Why is it thus mixed with them? As it is heavier than these 
gases, why does it not lie all along close to the earth with these 
above it, as water lies under the lighter oil when they are in a 
vessel together? It is because gases are so ready to mingle to- 
gether. The least motion will make them do it at once, and you 
know that there is always motion in the air. Even when it ap- 
pears to be still there is some motion, as you may know by the 
motes which you see flying about in the air in a still room as the 
sunbeams shining in reveal*them to your view. 

Gases mingle together as spirits of wine and water do. They 
are very different from oil and water in this respect. You may 
shake oil and water, and yet they will not mingle. The water 
will, after the shaking is over, take its place below the oil. But 
water and spirits of wine, or any kind of liquor, shaken together, 
will mix thoroughly, and stay mixed. So it is with the gases 
that make up the air. 

If you pour some alcohol or spirits of wine very carefully into 
a vessel partly filled with water, the water, which is heavier than 
the alcohol, will remain at the bottom. Just so the carbonic acid 
gas, which is heavier than the air, will remain very quietly at the 
bottom of a well when it is formed there. It is because the air in 
the well is so still. If you could shake up the air and the car- 
bonic acid as you can the alcohol and- water, you could make 
them mingle together. 



46 CARBONIC ACID. 



Grotto del Cane, or Dog's Grotto. 



See now what would happen if carbonic acid gas did not min- 
gle with the other gases of the air. Being heavier than they are, 
it would get below them, as water gets below air. It would make 
a sea of gas over the sea of water, covering all the valley s and 
plains. You see what would be the consequence to us and other 
animals. No animal, small or great, could live any where except 
on hills and mountains, for there only could he find any oxygen 
to breathe. 

There are some places on the earth where carbonic acid collects 
in large quantities. There is such a place in Italy, called the 
Grotto del Cane, or Dog's Grotto. The reason of this name you 
will soon see. On the floor of this grotto or cave there is always 
a layer of this gas. The layer is high enough to reach above the 
head of a dog, but not the head of a man. A man lives near by 
who shows the grotto to visitors, and, in doing this, he takes his 
dog in, who of course falls down senseless. He brings him out, 
however, quickly into the fresh air, which, with a dash of cold 
water, revives the dog, so that the same thing can be shown to 
the next visitors. But you can see by his leanness and the dull- 
ness of his eye that he is dealt with hardly ; for this gas, unlike 
nitrogen, is really poisonous. The dog falls senseless not merely 
for want of oxygen, but because the gas does him positive harm.* 

Where do you think the gas in this grotto comes from? It 
comes out from crevices in the rocks, being made somewhere in 
the earth near by. It is not uncommon for it to come out from 
such crevices and from cracks in the earth, and sometimes it bub- 

* To realize this difference between this gas and nitrogen, turn back to what I say 
about nitrogen on page 23. 



CARBONIC ACID. 



47 



Operation of the Grotto del Cane illustrated. 



bles up through the water of springs in the neighborhood of vol- 
canoes. Generally, however, it flies off in the air. Why, then, 
does it collect in this grotto? It is because it is so much shut in 
that the air does not circulate freely, and so some of the gas re- 
mains on the floor of the cave. 

The operation of the Grotto del Cane can be illustrated by 
Fi g. 20. a simple arrange- 

ment represented 
in Fig. 20. We 
have here a box 
with pasteboard, 
ABB, fastened all 
around the edges, 
variously cut and 
painted so as to 
represent rocks. 
The lower edge 
must, of course, 
have a piece of the 
pasteboard, A, to 
keep the gas from 
going out there. A hole is made on the top through which the 
taper can be let down into the imitation grotto. There is also a 
hole in the side for the pipe that brings the gas in from the bot- 
tle, 0. If you remember what I told you about obtaining car- 
bonic acid gas, you can tell what is in that bottle. On looking at 
this arrangement, you readily see that, as the air in the box is still, 
the heavy gas will quickly collect on the floor, being prevented 




48 CARBONIC ACID. 



Burning charcoal in close rooms. Carbonic acid in porter, champagne, etc. 

from flowing out by the pasteboard A at the lower edge. Of 
course the taper will not go out till it reaches near the floor. 

Persons are often injured by burning charcoal in a close room 
in an open furnace or chafing-dish, and sometimes death is occa- 
sioned in this way. It is the carbonic acid produced by the union 
of the carbon with the oxygen of the air that does this. As you 
understand about this, you can see that charcoal never ought to 
be burned in this way except in the open air, or in a room with 
the doors and windows open. You see, too, what the remedy is 
if we find any one poisoned by the gas from burning charcoal. 
It is to open wide the doors and windows to let the gas go out 
and mingle with the air, while fresh air comes in to take its place. 
Remember that doors must be opened as well as windows, for the 
air must come in along the floor to drive out all the gas. 

If a grown person and a child are in a room where charcoal is 
burned in an open furnace, the child will be affected first, because 
his mouth is so much nearer the floor than the mouth of the adult. 

There is considerable carbonic acid gas in porter, champagne, 
bottled cider, etc. It is this that bubbles up and makes the foam 
when the cork is drawn. Where is it before we draw the cork ? 
If you hold the bottle up to the light, you see nothing there but 
the liquid. But the gas is all there. Its particles are all crowd- 
ed in and concealed among the particles of the liquid. The gas 
is imprisoned, as we may say. But when we draw the cork it 
is set at liberty, and, as it comes out eagerly and quickly to the 
air, it carries up some of the liquid with it, making a froth. In 
what is commonly called soda-water there is no soda, but it is 
water into which carbonic acid gas has been thrown by a fore- 



CARBONIC ACID. 49 



What soda-water is, and how it is made. 



ing-pump. We sometimes, however, make soda-water with two 
white powders. We dissolve one in some water in one tumbler, 
and the other in water in another. Pouring them together, we 
have an effervescence, which I will explain to you. One of the 
powders is a carbonate of soda ; that is, carbonic acid united with 
soda. The other powder is tartaric acid, which likes soda better 
than carbonic acid, just as, in obtaining carbonic acid (page 37), 
muriatic acid likes lime better than the carbonic acid does. The 
tartaric acid .therefore takes the soda, and the carbonic acid set 
free goes up so quickly through the water as to cause the effer- 
vescence. 

Well, when we drink soda-water, beer, etc., we take some of this 
gas into the stomach ; but, poisonous as it is when it goes into our 
lungs, it not only does no harm in the stomach, but is refreshing, 
and does* us good. 

Questions. — Explain Fig. 17. Tell about the fire in a coal-mine. What is said 
of the collection of carbonic acid gas in wells ? How can we find out whether there 
is any in a well ? What is the first expedient mentioned for removing it from a 
well? What is the second expedient mentioned ? Show how this operates by Fig. 
19. Mention the third expedient, and explain it. Why not throw the lime dry 
into the well ? Why does not the heavy carbonic acid gas keep under the oxygen 
and nitrogen in the air ? Give the illustrations in regard to spirit and water, and 
oil and water. Give the comparison in regard to carbonic acid in a well and the 
water in a jar with alcohol carefully poured upon it. What would happen if the 
gases in the air did not readily mingle together? What is said of the Grotto del 
Cane ? What is the source of the gas in this grotto and in other places ? Why 
does it collect in this grotto? Explain Fig. 20. What is said about burning char- 
coal in close rooms ? What would you do if you found any one poisoned in this 
way? Tell about the grown person and the child. What is said of carbonic acid 
in porter, bottled cider, etc. ? What is soda-water? Explain the operation of soda 
powders. What is said of the effect of this gas on the stomach? 

d 



50 THE AIR. 



Quantity of carbonic gas in the air. How the air is affected by fires and lights. 



CHAPTEE VIII. 

THE AIR. 

I have already told you nmcli about the air, but we will now 
consider its composition more particularly. 

You have learned much about the three gases of which the air 
is composed. The largest part of the air is nitrogen, there being 
about four times as much of it as there is of the oxygen. Of car- 
bonic acid there is a very small proportion, as you realized on 
looking at the figure on page 31. Yet there is really a great 
quantity of this gas in the whole of the air, for you must remem- 
ber that the atmosphere is 45 or 50 miles high. It is calculated 
that over every acre of land there are seven tons of carbonic acid 
gas. 

There are continual additions made to the carbonic acid in the 
air in various ways. Every fire or light that burns adds to it; 
for, as you learned in Chapters Y. and VI., the burning carbon in 
wood and other substances unites with the oxygen of the air, and 
forms carbonic acid gas, which flies off. 

You see that the fire or light lessens the oxygen of the air at 
the same time that it adds to the carbonic acid. If you put a can- 
dle under a glass jar placed on a smooth plate with its open end 
downward, it will burn brightly at first, because there is enough 
oxygen in the air inclosed in the jar; but soon it will burn dim- 
ly, and, after a while, go out. The reason is that the carbon of 
the candle uses up the oxygen by uniting with it to form carbon- 



THE AIR. 51 



Making chalk with the breath. Quantity of charcoal in the breath. 

. , : . 

ic acid. If, just as the candle is about to go out, you lift up the 
jar, the flame of the candle will brighten up again, because you 
let out some of the carbonic acid, and the fresh air that comes in 
supplies the candle with oxygen. 

You see, then, that all fires and lights lessen the oxygen in the 
air, and add to its carbonic acid. 

Then, too, every animal is breathing out carbonic acid from its 
-lungs. This you can prove in your own case by a simple experi- 
ment. Put into a tumbler or bowl some lime water. With a 
tube breathe into this, and you will find, after a little time, that 
the lime water has become quite milky. The reason is that the 
carbonic acid which came out from your lungs has united with 
the lime of the lime water, and formed carbonate of lime, or 
chalk. After standing a little while the water will become clear, 
the chalk having settled at the bottom in a fine powder. This 
will remind you, I presume, of another instance mentioned before, 
in which lime and carbonic acid were introduced to each other so 
that they might unite. I refer to one of the expedients for get- 
ting a well rid of the carbonic acid in it. Try to recollect it ; but, 
if you can not, turn to it on page 44. 

The quantity of carbonic acid which we breathe out in twenty- 
four hours is considerable. It is calculated that a full-grown 
man breathes out in twenty -four hours over two pounds of car- 
bonic acid, and in this there is over half a pound of solid carbon 
or charcoal. He throws off, therefore, from his lungs, in the 
course of a year, nearly 200 pounds of charcoal — considerably 
more than his weight, even if he be quite a large-sized man. 

As all animals, of every size, from the elephant down to the 



52 THE AIR. 



How droTrning destroys life. Experiment with a mouse. 
+ 

smallest insect, are all the time breathing out carbonic acid gae 7 
the supply of this gas to the air must be very great from this 
source. 

All animals also take in oxygen from the air with every breath. 
It goes into their blood, and becomes a part of it. Your blood 
could not keep you alive if it did not constantly receive oxygen 
into it as it runs through the lungs. When any one dies by drown- 
ing, he dies merely because no oxygen can get into the blood. 
The water prevents it from getting there by shutting out the air in 
which the oxygen is. You see, then, how proper it is to speak 
of oxygen, as I did on page 16, as the lung-food of the body. 

See now how the air which you breathe out differs from that 
which you breathe in. That which you breathe out has less oxy- 
gen and more carbonic acid. The nitrogen is not altered. Just 
as much of this comes out as goes in. 

If you put a mouse or any animal into a glass jar, and close it 
tight, so that no fresh air can get into it, he will, after a little 
while, die, just as the candle went out under the same circum- 
stances, as noticed on page 50. He dies, too, for the same reason 
that the candle went out. He adds, by his breathing, to the car- 
bonic acid in the jar, and lessens the oxygen. If, when he is 
about to die, you let in some fresh air, he will revive, for the same 
reason that the expiring candle brightened up on raising the jar 
placed over it. 

I will tell you a story of an emigrant ship called the London- 
derry, which will illustrate the same thing. The ship was crowd- 
ed with poor emigrants, and many of them were up on deck. 
There came on a terrible storm, and the captain ordered them all 



THE AIR. 53 



Story of the Londonderry. Breathing of leaves. 

to go below into the cabin. Here they were very much, crowded 
together, and the only fresh air they got came to them through an 
opening in the deck ; and as the sea- water dashed down through 
this in great quantities as the waves broke over the vessel, the 
captain ordered that tarpaulin (cloth through which neither water 
nor air can pass) should be nailed over it. The people below im- 
mediately suffered dreadfully for want of fresh air. The poison- 
ous carbonic acid increased in quantity every time they breathed, 
and none of the pure air could get into them. They cried out in 
their distress, but the noise of the storm prevented their being 
heard. At length one of the emigrants succeeded in forcing a 
hole through the tarpaulin. He told the captain that the people 
were dying for want of air. The tarpaulin was pulled up at 
once. Many were already dead, and many were just about to 
die. The fresh air saved many of the latter, just as letting in 
fresh air into the jar revived the expiring flame of the candle. 

All animals, then, in their breathing, and all fires and lights in 
their burning, add to the carbonic acid in the air and lessen the 
oxygen. What is there, then, to hinder the air from becoming all 
the time more and more loaded with carbonic acid, and less and 
less supplied with oxygen ? Just here comes in a wonderful and 
beautiful provision of the Creator. He has provided the means 
of taking away carbonic acid constantly from the air, and of sup- 
plying it all the time with fresh oxygen. If it were not so, all 
animals would die, and all fires and lights would go out. And 
what, think you, are the agents that God has appointed to do this 
work ? It is the leaves ; they breathe, but their breathing is dif- 
ferent from that of lungs. Their breathing is different in this : 



54 THE AIR. 



How the breathing of leaves differs from that of lungs. 



animals that are not small you can see breathe — you can see the 
chest move ; but in the very largest leaves that you can find, as 
the leaves of corn or the pumpkin vine, you never see any motion 
in the breathing. They are very still in their breathing. But 
the greatest difference is in another thing. While lungs, in their 
breathing, give out carbonic acid, the leaves take it in ; and while 
lungs take in oxygen, the leaves give it out. Every leaf that you 
see gleaming in the sun is busy pouring out into the air oxygen 
from all its little pores, and taking in, at the same time, carbonic 
acid gas. 

I have told you what becomes of the oxygen that is absorbed 
by the blood in the lungs; but what becomes of the carbonic 
acid which the leaves absorb? This furnishes carbon for the 
growth of the plant. You learned in Chapter Y. that carbon is 
one of the chief ingredients of wood. Now a very large part of 
this carbon is taken in by the pores, or little open mouths on the 
leaves. These are spread out like nets to catch the carbon float- 
ing in the air in the carbonic acid gas, and this is carried to all 
parts of the plant to help it grow. Whenever you are looking, 
then, at a large tree, just think how a great part of that solid trunk 
was once moving about in the air, and was caught up by millions 
upon millions of little mouths in thousands upon thousands of 
outspread leaves. Think, too, that perhaps some of that hard 
wood was once in your soft breath coming out from your lungs. 
Even the little insect that hums among its leaves may have fur- 
nished some, a little, of the carbon which is in the tree. 

The carbon which you breathe out from your lungs is scattered 
about, and goes to leaves far and near. But suppose it went to 



THE AIR. 55 



The exchange between lungs and leaves. How this is in winter. 

the leaves of one tree alone, how much carbon do you think your 
lungs would give to the tree in a year ? More than the weight 
of your whole body, and that would be enough to make quite a 
large branch. 

You see, then, that there is a regular exchange going on be- 
tween leaves and lungs every where ; lungs give carbon to leaves, 
and take back oxygen in exchange. But how is this in winter, 
when there are no leaves except upon the evergreens? Do these 
leaves take up all the carbon that is breathed out then? No, 
there are not enough of them to do this. Does the carbonic acid 
then increase in the air, and the oxygen lessen ? Not at all. It 
is now just as it is in summer, when the leaves are all alive and 
breathing. I will tell you how this is. You remember how I 
told you that the gases were very ready to mix up with each oth- 
er, especially when they are shaken together. Now every motion 
of the air, every gust of wind, shakes up the gases that compose 
the air, and scatters the carbonic acid gas that arises any where 
in every direction. This gas therefore, we may say, flies on the 
wings of the wind, and, breathed, out in one place, it may thus 
find its way to many places, not merely miles, but thousands of 
miles distant. That which is breathed out at the north in winter 
may go to the south to be drank up by leaves there, while these 
sunny climes send up oxygen for the lungs of the north. 

The oxygen and the carbonic acid in the air, you see, are contin- 
ually changing. The oxygen is constantly used up by being ab- 
sorbed by lungs, and by uniting with substances that are burning. 
At the same time, fresh oxygen is poured forth from the leaves of 
all plants into the air; so also the carbonic acid is continually 



56 THE AIK. 



Free air the same in all places. How it is with air in close, crowded rooms. 

changing, being absorbed by the leaves, while new carbonic acid is 
supplied from the lungs of all animals, from fires and lights, etc. 

Now in the midst of this change the air in all parts of the earth 
has always exactly the same proportions of the three gases. If a 
gallon of air from Europe, and another from Asia, and another 
from Africa were brought here and examined by a chemist, he 
would find that each of them had the same amounts of nitrogen, 
and oxygen, and carbonic acid that a gallon of American air has. 
How wonderful this is ! In this exchange which is going on be- 
tween the leaves on the one hand, and lungs, fires, and lights on 
the other, how is this balance so nicely kept ? We do not know ; 
but the Creator understands it, and he has all power, and so se- 
cures this regularity even in so changing a thing as air. 

But what I have just said about the air is true only of that 
which is out of doors, free to go " where it listeth." When it is 
shut up the proportions of its ingredients may be very much 
changed. Suppose there are a great many persons crowded into 
a small close room; their lungs are using up the oxygen and 
pouring out carbonic acid gas. A little fresh air gets in at cracks 
and loose places about the windows and doors, but this is not 
enough to prevent the air in the room from losing a great deal 
of its oxygen, and becoming loaded with carbonic acid. For this 
reason, the lights, after a while, burn dimly, and the people be- 
come dull and drowsy. A gallon of air taken from this room at 
such a time would be very different from a gallon taken from the 
air outside. It would have just as much nitrogen in it, but much 
less of the life-giving oxygen, and much more of the poisonous 
carbonic acid. 



THE AIR. 57 



Destruction of life by want of ventilation. 



Think now what happens when the doors of such a room are 
opened and the people go out. The carbonic acid flies off at once 
in the air, diffused far and wide, to be drank up by the mouths in 
the leaves, and the fresh air rushes in to supply its place. 

Great harm is done to the health of people by breathing air 
that is so loaded with carbonic acid. It may not be felt much at 
the time ; but if such air be breathed often, a little harm done each 
time will, after a while, amount to a great deal. A few persons 
were quickly killed on board of the Londonderry, but a multi- 
tude of people are killed every year by breathing bad air in rooms, 
and yet they do not know it, because it is done so slowly. 

Questions. — What are the gases in the air? What is said of the quantity of car- 
bonic acid in the air ? What effect have fires and lights upon the carbonic acid of 
the air ? What upon its oxygen ? How does a candle burning under a glass jar 
illustrate this ? How does the breathing of animals affect the carbonic acid of the 
air ? Give the experiment with lime water. How is this like one of the expedients 
for removing carbonic acid from a well ? What is said of the quantity of carbon 
thrown off from the lungs ? What of the supply of carbonic acid to the air from 
the lungs of all animals ? What is said of the taking in of oxygen by the lungs ? 
How is death caused by drowning ? How does the air which we breathe out differ 
from that breathed in ? Give the experiment with the mouse. State the compari- 
son about the candle. Tell the story of the emigrant ship. How does the air con- 
tinually keep the same quantity of carbonic acid and oxygen ? What is said of the 
breathing of the leaves ? What is done with the carbonic acid which the leaves ab- 
sorb ? How much carbon do you give to the leaves ? What is said of the exchange 
between lungs and leaves ? How is it with this exchange in winter ? What is said 
of the constant change in the carbonic acid and the oxygen of the air ? What is 
said of the preservation of uniformity in the midst of this change ? What is said of 
the air of a close room containing many persons ? What is done with this air when 
the doors are opened and the people go out? What is said of the injury to health 
from breathing bad air ? 



58 



HYDROGEN. 



Composition of water. 



CHAPTER IX. 

HYDROGEN. 

"Water is composed of two gases. One of these is oxygen, of 
which you have learned so much in previous chapters ; the other 
is hydrogen. This is the lightest of all gases, and therefore the 
lightest of all substances. Air is fifteen times as heavy as hydro- 
gen. A balloon, therefore, filled with this gas goes up very swift- 
ly in the air. 

As hydrogen is the lightest of all substances, a metal called pla- 
Fi g . 21. tinum is the heaviest. Fig. 

H ydroge n. 21 exhibits the comparative 

TLatvnumi, weights of four substances, 
• platinum, water, air, and hy- 

drogen. The little shot of 
platinum equals in weight 
the balls or spheres of wa- 
ter, air, and hydrogen repre- 
sented in the figure. 

In every nine pounds of 
water there are eight of ox- 
ygen gas and only one of 
hydrogen. But as oxygen is sixteen times as heavy as hydro- 
gen, the bulk of the hydrogen that goes to form any portion of 
water is twice as great as that of the oxygen in it. This may be 



V/ater. 

O 




HYDKOGEN. 



59 



Water formed by burning hydrogen and oxygen together. 



represented by Fig. 22. 

Fig. 22. 



The smaller space represents the oxy- 
gen. It is divided into eight spaces to 
represent the eight pounds. Now as 
hydrogen is only one sixteenth the 
weight of the same bulk of oxygen, it 
will take sixteen such spaces to repre- 
sent the one pound of hydrogen, and 
this will make a figure containing twice 
the space of that representing the eight 
pounds of oxygen. 

Hydrogen will burn with a brisk but faint flame, giving but 
little light. How strange it seems that oxygen, that makes other 
things burn, and hydrogen, a gas that itself burns, united togeth- 
er, form a liquid that puts out fire ! 

What will seem stranger still to you is that, when hydrogen gas 
is burned in oxygen, water is formed. In the burning, the oxy- 
gen and the hydrogen unite together. Not a jot of either of them 
is lost, just as none of the carbon and oxygen are lost when car- 
bon is burned in oxygen ; they merely go into a new condition, 
uniting to form a liquid. In doing this, the bulk of both of them 
is made much smaller. It takes a great deal of these gases to 
form a very small amount of water. You will realize this by 
looking at Fig. 21, remembering that oxygen is nearly of the same 
weight with air. It will take, of hydrogen and oxygen mingled 
together, an amount only a little less than that representing hy- 
drogen in the figure to make a drop of water of the size repre- 
sented. 

If hydrogen be burned in air, we have the same result as when 



60 



HYDROGEN. 



Catching water from a burning candle. 




it is burned in oxygen. The hydrogen unites with the oxygen 
of the air and forms water. It will have nothing to do with the 
nitrogen that is in the air, but lets it alone, and takes the oxygen 
and combines with it. You can see that water is formed by the 
Fig. 23. burning of hydrogen in air by various ex- 

periments. One is represented in Fig. 23. 
This figure you have seen before, in the first 
chapter, and the experiment was then part- 
ly explained. You are now prepared to un- 
derstand a fuller explanation of it. There 
are carbon and hydrogen united together in 
the tallow. Yes, this lightest of all the gas- 
es helps, in this case, to form a solid sub- 
stance. As the melted tallow goes up the wick, the air brings 
oxygen to it all around, and the heat makes this oxygen unite 
with both the carbon and hydrogen of the tallow. By uniting 
with the carbon it forms carbonic acid. This is, you know, a col- 
orless transparent gas, and so you do not see it. But there it is 
in the jar. Uniting with the hydrogen, the oxygen forms water. 
This goes up in vapor with the carbonic acid, and so also you do 
* not see that. But this vapor soon collects on the inside of the 
glass, because it is cool. The glass therefore becomes dim, and 
after a little time there is enough water there to form drops and 
trickle down into the plate. 

In Fig. 24 you have another experiment. Here hydrogen alone 
is burned without carbon. The bottle that you see contains the 
materials for making the gas, of which I will tell you soon. The 
flame of the hydrogen passes into the horn-shaped glass. The va- 



HYDROGEN. 



61 



Readines3 of hydrogen and oxygen to unite. 



How hydrogen is obtained. 



Fig. 24. 




por formed there by the 
virion of the hydrogen 
with the oxygen of the 
air passes into that long 
glass vessel, and there is 
condensedj as you see, in 
drops. 

You see how ready 
oxygen is to unite .with 
hydrogen. But you re- 
member that, in a previous chapter, I have told you that the 
oxygen and nitrogen in the air would not unite, however much 
they were heated and shaken together; nothing but lightning 
can make them unite. You see one reason for this difference. 
If the oxygen and nitrogen in the air could be easily made to 
unite, very bad effects would be experienced, as I told you in 
Chapter III. But. when oxygen unites with hydrogen the result 
is water, which will do no harm. Water we want in abundance. 
We want it in the air as well as every where else, for dry air would 
be very uncomfortable and injurious to us. It is the water in 
the air, in the form of unseen vapor, that makes the air so soft 
and pleasant to us. But nitric acid, and the other compounds of 
oxygen and nitrogen, we do not want in the air, and if much of 
them were there they would destroy every living thing. 

I will now tell you how hydrogen is obtained. We put into a 
retort, or a bottle, some bits of zinc, some water, and a little sul- 
phuric acid, which is commonly called oil of vitriol. Now the 
acid makes the oxygen of the water unite with the zinc, and the 



62 



HYDROGEN. 



^ ; u Philosopher's candle." 



Affinity of oxygen for iron. 



Fig. 25. 



hydrogen of the water is therefore set free. This rises and passes 
out of the vessel, carrying the air that is in the vessel along with 
it ; and soon, when all the air is driven out, the 
gas comes out alone. In Fig. 25 is represented 
what is called the " philosopher's candle." The 
zinc, water, and sulphuric acid are in the bottle, 
which is fitted with a cork having a tube in it. 
The gas issuing from the tube burns just as illu- 
minating gas does issuing from a gas-burner. 
There is some caution required in making this gas 
in this way, for a mixture of it with common air is 
explosive. If, therefore, you should hold a light 
H§lE~ to the tube before the air is driven out, you might 
have an explosion, and your bottle might be 
broken and its contents scattered about. 

One way in which hydrogen is obtained shows how well oxy- 
gen likes iron. The apparatus is represented in Fig. 26. You 




Fig. 26. 



see a furnace, C, with 
an iron pipe, B B, run- 
ning through it, like 
a gun-barrel. In this 
pipe are put fine scrap- 
ings of iron or bits of 
needles. At one end 
of this pipe is another 
pipe from a flask of 
water, A, and the water is heated by a spirit-lamp under the 
flask. As the water boils, steam passes through the iron pipe in 




HYDROGEN. 63 



Carbonic acid and hydrogen contrasted in regard to weight. 



the furnace. Now steam is water, but very finely divided up, as 
we may say. As it passes through the red-hot pipe among the 
turnings of iron, the oxygen of the water is made by the heat to 
unite with the iron, and form rust. It parts company, therefore, 
with the hydrogen of the water, and so the hydrogen goes out 
alone through the other end of the pipe. You see it passing into 
the glass jar, D, in the pneumatic cistern. 

You remember what I said about pouring carbonic acid gas 
downward. You can not do this with hydrogen. It is so light 
that, the moment it escapes from a vessel, it passes directly and 
Fig. 2t. quickly upward. You can let a jar of car- 

bonic acid gas stand, and the gas will not 
go out ; but if you set down a jar of hy- 
drogen gas with its mouth upward, the gas 
will at once pass out, the air coming in to 
take its place. If you want to pour hydro- 
gen gas from one jar into another, you must 
hold them in the manner represented in Fig. 
27, the upper jar being the one which is to receive the gas. 

I will make some comparisons between liquids and gases in these 
respects. If you should set a jar filled with the liquid metal 
mercury all over in water, the mercury would remain in the jar, 
for the same reason that carbonic acid does not rise out of the jar 
when left to stand in the air. As the carbonic acid is heavier 
than air, so is the mercury heavier than water. On the other 
hand, if you introduce a jar of oil into water, the oil will go up 
out of the jar, the water taking its place, as hydrogen gas goes up 
out of a jar set down in air, the air going in to take its place. 




64 



HYDROGEN. 



A contrast. 



Squeaking toy in hydrogen. 



Fig. 2S. 




And as hydrogen will stay in a jar 
held in air with its mouth down- 
ward, so will oil stay in a jar im- 
mersed in water with its mouth 
downward. 

If you set fire to the hydrogen 
in a jar, the manner of its burning 
differs according to the ways in 
which you hold the jar. If you 
hold it with the mouth upward, 
the gas, rapidly rising as it burns, 
bursts upward with a large flame, 
as seen in the jar A, Fig. 28. But 
if you hold it with the mouth down- 
ward, the gas burns very quietly 
as it issues 



HIIl ill / slowly from 

the mouth, 
as seen in 
the jar B. 
Here the gas 
does not come out freely, because, from its 
lightness, it is not disposed to come down 
from out the jar. 

As hydrogen is so light and thin a gas, 
it has a very curious effect upon sounds. 
If what is called the squeaking toy is made 
to utter its voice in a jar of hydrogen as 
represented in Fig. 29, the sound is very ludicrous. 



Fig 29. 




HYDROGEN. 65 




Music from burning hydrogen. Illuminating gas. Why gas does not smell in burning. 

_Fi g . 30. Musical sounds can be made by burning this gas 

in glass tubes, as represented in Fig. 30. These 
sounds vary according to the sizes of the tubes. 
They vary also as you raise or lower the tube. 
Great amusement can be afforded by the variety 
of sounds which can thus be produced. 

Burning hydrogen gives but a faint light ; but 
the light of the gas that we burn in our houses is 
very bright, and yet it is partly hydrogen. The 
reason that it gives so bright a light is that there 
is carbon or charcoal united with the hydrogen. 
It is on this account that it is called by the chemist carbureited 
hydrogen. As you watch the flame from a gas-burner, you see 
little bright points all the time sparkling upward. These are oc- 
casioned by the burning of the minute particles of the carbon. 

In the burning of illuminating gas, the oxygen of the air, as in 
the case of the candle, unites with both the carbon and the hy- 
drogen, forming, with the carbon, carbonic acid gas, and with the 
hydrogen, water. And if you hold a glass jar over the burner, 
the watery vapor will condense on the inside of the jar, as in the 
case of the candle. 

When the gas escapes without burning, it smells, you know, 
very disagreeably ; but when it is burned you do not smell it at 
all. Why ? Because it is used up by the oxygen of the air in 
forming water and carbonic acid, and neither of these have any 
smell. The smell of the gas is useful to warn us of danger. If it 
had no smell, whenever there is a leak of gas we could not know 
it, and might' take a light into some place where there is a great 

E 



66 HYDROGEN. 



What is to be done when gas has escaped. 



deal of it. An explosion would be the consequence, and great 
harm would be done, and perhaps lives lost. As it is now, when 
there is a leak we smell the gas, and open all the doors and win- 
dows, and let them be open for some time before we go in with a 
light. 

Questions. — Of what is water composed ? What is said of the lightness of hydro- 
gen? What is the heaviest of all substances? Explain Fig. 21. What are the 
proportions by weight of oxygen and hydrogen in water ? What are their propor- 
tions in bulk ? Explain Fig. 22. What is said of the difference between water and 
its ingredients ? What is formed when hydrogen is burned in oxygen ? What is 
said of the amount of these gases required to form water ? What is said of burning 
hydrogen in air ? What two things are formed when a candle burns ? Explain 
Fig. 23. Explain Fig. 24. What is one reason why the Creator has made oxygen 
and hydrogen so ready to unite ? Give the contrast in relation to the union of oxy- 
gen with nitrogen. How can we obtain hydrogen? Describe the "philosopher's 
candle." Describe and explain the second mode given of obtaining hydrogen. State 
the contrast between hydrogen and carbonic acid. Give the comparisons between 
liquids and gases. Explain Fig. 28. Tell about the squeaking toy. What is said 
of burning hydrogen in glass tubes ? Give the difference in burning between hydro- 
gen and illuminating gas, and the reason of the difference. What are formed in 
the burning of illuminating gas, and how ? Why does the smell of this gas disappear 
in burning? How is this smell useful? 



COMBUSTION. 67 



What combustion is. Busting of iron a slow fire. 



CHAPTER X. 

COMBUSTION. 

I have already had considerable to say about burning, or com- 
bustion, but now I shall go into the subject more particularly. 

What we usually call combustion attends, as you have seen, 
the uniting of oxygen with some other substances, as the solid, 
carbon, and the gas, hydrogen. Thus, when we have a combus- 
tion of charcoal, the oxygen unites with the charcoal ; when hy- 
drogen burns, oxygen unites with the hydrogen ; and when iron 
burns, as you have seen that it does freely in 'a jar of oxygen gas, 
oxygen unites with the iron. 

But we commonly use the term combustion only when there 
are both heat and light, and yet the union of oxygen with other 
things often takes place without producing any light. This is 
when the union takes place slowly. Thus, when iron rusts, the 
oxygen of the air unites with it, but it does it so slowly that no 
light is given out ; there is heat, but so little of it that it can not 
be felt because the union is so slow. It is a very slow fire. Now 
this same union takes place when iron or steel burns in oxygen, 
and then we have both heat and light, because the union is so 
quickly effected. It is really a combustion in both cases. The 
only difference is that in the one case it is quick, and in the other 
it is slow. When a man, then, paints his iron fence to keep it 
from rusting, he really keeps it from getting burnt. 

You can understand now how water puts out fire. It shuts 



68 COMBUSTION. 



How fires are extinguished. Notions of people about it. 

out the oxygen of the air from the burning substance. It does 
the same to it that the paint does to the iron. But perhaps you. 
will say that there is a plenty of oxygen in water, as it is com- 
posed of oxygen and hydrogen, and throwing water on fire is 
therefore giving it oxygen. Not at all. Oxygen is not in water 
as oxygen ; it. has formed a new substance with hydrogen, and 
the hydrogen in this new substance holds on to the oxygen, so 
that the fire can not get a particle of it. 

When you put out a fire by smothering it, you put it out real- 
ly very much in the same way that you do when you pour water 
upon it ; you shut out the oxygen of the air, and the burning 
stops merely for the want of oxygen. So, if a person's clothes 
take fire, you need not wait to get water, but wrap around at once 
whatever is at hand— a coat, a rug, or any thing else — thus shut- 
ting out the oxygen of the air. An extinguisher put over a can- 
dle puts out the light by keeping oxygen from coming to it. 

The notions of people about putting out fire commonly fall far 
short of the real explanation. The following is a very fair speci- 
men of these notions. I once asked some young pupils how wa- 
ter puts out fire. "That is plain enough," said one ; " it quench- 
es it." "But how?" asked I. "It is just the opposite of fire," 
said another. "But how opposite?" asked I. "Because it is 
cold, and fire is hot," said he. " But," said I, " hot water can put 
out fire." "Well, it smothers the fire," said another. He came 
the nearest to a right answer, but he had no idea of what smoth- 
ering really is. I trust that you, however, have a correct idea of 
the explanation which I have given of it, and that you will not 
hereafter use the word without knowing what it means. 



COMBUSTION. 69 



Blowing a fire. Blowing out a candle. 

As fire, or combustion, comes from the union of oxygen with 
the burning substance, the more freely you can bring the oxygen 
to it, the more free and bright will be the fire. When you blow 
a fire with bellows to make it burn, you bring the oxygen of the 
air to it faster than it would come without the blowing. The 
coals, perhaps, are just glimmering — kept alive, as we say, that is, 
kept on fire — by the little oxygen that is in the still air about 
them. You blow them, and you bring a great deal more of air, 
and therefore of oxygen, to them, and they brighten up at once. 
If you could blow nitrogen alone, or carbonic acid gas, upon them, 
it would put them out, for this would keep away from them the 
oxygen of the air. 

A burning candle is a fire, and oxygen keeps it burning ; the 
more oxygen, therefore, that you bring to it, the brighter should 
it burn. Why, then, is it that you blow a candle to put it out? 
A boy once supposed that he had given a sufficient explanation 
in saying that the breath, as you blow, knocks the flame right 
over. The true explanation is this : A certain amount of heat is 
needed to keep up the burning. Now the air may be thrown so 
rapidly against the candle as to carry off the heat enough to stop 
the combustion ; it carries off heat as air carries off heat from 
your face when blown against it by a fan. In blowing a fire that 
is just starting we have to be a little careful, or we may blow 
away the heat too much from the fire. 

We have some contrivances for making our lights burn very 
brightly. The object of them is to supply oxygen rapidly, but 
at the same time steadily, and not by sudden blasts. One of these 
contrivances is a glass chimney. See how this operates. The 



70 COMBUSTION. 



Operation of lamp-chimneys explained. 



hot gas and vapor that come up from the light are confined in 
the chimney instead of spreading out in the air around; they 
pass up, therefore, very rapidly through the chimney, and so make 
a strong draught,* as we say. This makes the air come rapidly 
to the light from below, and of course a great deal of oxygen 
comes to it in a little time. 

You see how great the draught is if you hold your hand over 
the top of the chimney ; you will feel a current of hot gas and 
vapor striking against it. You must be careful not to put your 
hand too near. This current does not all of it go straight up, but 
it spreads out as soon as it escapes from the chimney, so that, at 
a little distance, your hand feels only a small part of the current, 
and that is somewhat cooled. 

Another contrivance is to have the wick flat instead of round. 
You see that such a wick presents a larger surface to the air than 
a round one, and therefore more of it can be reached by the oxy- 
gen. 

Some wicks are made circular, the air being admitted on the 
inside as well as the outside of the circle. A very bright light is 
made in this way. 

Observe now how we start a fire. Commonly we do it by put- 
ting something burning to the combustible substance. Thus we 
set fire to wood by burning paper or shavings. So, as we open a 
gas-burner, we put to it a burning match, and thus set fire to the 
stream of gas as it comes out. But think a moment what sets 
fire to the match. It is rubbing it, you will say. But how? 

* The manner in which this draught is produced is explained fully in the chapters 
on Heated Air and Chimneys, in the Third Part of the Child's Book of Nature. 



COMBUSTION. 71 



How things are set on fire. Why some things burn more easily than otherg. 

The friction creates heat enough to cause the oxygen to unite 
with the phosphorus, and the union is quick enough to make 
light as well as heat. So you see that it is heat that causes what 
we call fire. 

You can see this very often in kindling a wood fire. Suppose 
you have a bed of coals underneath the wood which is placed on 
the andirons, how is the wood set on fire ? The coals heat the 
wood, and, after a little time, they make the wood hot enough to 
set it on fire. Here no flame goes from the coals to the wood, 
but only heat. 

Now why is it that some substances take fire so much more 
easily than others ? Why, for example, does a match with phos- 
phorus on its end take fire by friction, while one dipped in sul- 
phur will not, but must have fire touched to it ? It is because 
the phosphorus has a greater liking or affinity for oxygen than 
sulphur, and therefore it requires less heat to make them unite. 
So charcoal has an affinity for oxygen, but not so much that you 
can make them unite by rubbing the charcoal. Phosphorus has 
a greater affinity for oxygen than any of the substances that I 
have yet told you about ; it therefore takes fire so easily that you 
have to be very careful in handling it. But in another chapter I 
shall tell you about a substance, a metal, that likes oxygen so well 
that, if you put it into water, it will steal the oxygen from the hy- 
drogen and unite with it, and the union is so quick that it sets 
the hydrogen all ablaze. 

There are some substances that can not be burned at all. Gold 
is one of them. Iron, you have seen, can be burned j that is, it 
can be made to unite with oxygen ; but you may expose gold to 



72 COMBUSTION. 



Contrast between gold and iron in regard to combustion. 



the hottest fire that you can make, and it will only melt. It will 
not burn. It will not unite with the oxygen that is all around it. 
It has no liking or affinity for oxygen, as iron has. And what is 
true of these two metals in regard to quick combustion, is also 
true of them in regard to the slow combustion that I spoke of in 
the first part of this chapter. Gold never rusts in the air ; that is, 
it does not burn up with a slow fire, as iron does. 

Questions. — What occurs usually in what we call combustion? Illustrate the dif- 
ference between quick and slow combustion. Why are iron fences painted ? How 
does water put out fire ? Why does not the oxygen that is in the water make the 
fire burn ? What is said of putting out fires by other means besides water ? Give 
the conversation related about putting out fire. Explain the effect of blowing a fire 
with bellows. What would be the effect if you should blow nitrogen or carbonic 
acid upon a fire ? Explain the operation of a glass chimney on a lamp. If you 
hold your hand over the top of the chimney, what strikes against it ? What is the 
advantage of a flat wick ? What of a circular one ? When we set fire to any thing, 
what is it that starts the fire ? Give the illustration of the match ; also of the wood 
set fire by coals. Tell what affinity has to do with producing fire. What is said 
about the affinity of phosphorus for oxygen? What about the aflinity of a certain 
metal for it ? 



GAS-MAKING AND GAS-BURNING. 73 



Chemistiy of a candle. 



CHAPTER XI. 

GAS-MAKING AND GAS-BURNING. 

Every candle or lamp is a gas factory. I will show you how 
this is in the common candle. 

I have told you that there are both carbon and hydrogen in 
the tallow. They are united together there as a solid compound ; 
but, as the candle burns, this solid becomes by the heat a liquid 
at the foot of the exposed part of the wick. See what a cup of 
melted tallow we have there. It is curious to observe how this 
cup is formed, and kept just so, all the time that the candle is 
burning away. The heat of the burning wick melts the tallow, 
but that which is nearest the wick is of course melted first. This 
keeps a raised edge ail around. If the wick gets bent over to 
one side, it is apt to melt this edge on*that side, and so some of 
the melted tallow runs out of the cup and down the side of the 
candle. 

But the melted tallow at the foot of the wick must go up the 
wick to be burned. How is this? It goes up because there is 
an attraction between the wick and the liquid, and therefore the 
particles of the liquid go up every where among the fibres of the 
wick. This kind of attraction is commonly called capillary at- 
traction, because it was first particularly observed on putting the 
ends of very small tubes in water, or almost any liquid. The 
smaller the tube was, the higher the liquid was observed to go 
up in it. The small tubes were called capillary tubes because 



74 GAS -MAKING AND GAS-BURNING. 

Flame of a candle burning gas. Unburned gas inside of it. 

their bores were as fine as hairs, capilla being the Latin word for 
haii> 

The liquid tallow, when it comes to the lower part of the flame, 
is changed by the heat into a gas, and it is the burning of this gas 
that makes the flame. What is this gas? It is hydrogen gas 
charged with carbon. It is very much the same gas with that 
which comes out of a gas-burner. 

The flame of a candle is a curious thing to examine. It is not 
really all flame ; a part of it is gas, which is not burning. If you 
look carefully at the flame when the air is still, you will see that 
it is hollow, like a shell. Now the space inside of this shell is 
filled with gas which is not yet on fire ; this looks dark, as you 
see it through the bright shell of flame. 

You can prove that this dark inner part is gas by some very 
m 31 pretty experiments. Here is one. Take a 

small glass tube, and put one end of it, as you 
see in»Fig. 31, in the very middle of the flame 
— -in the dark part. Some of the unburnt gas 
will pass off through the pipe, and you can 
set it on fire as it issues at the other end, as 
represented. Every candle, you perceive, then, 
is a gas factory, and you can take the gas from 
it in pipes, as we do from the large gas facto- 
ries that supply towns and cities. 

You can thrust a match directly into this inner dark part of 
the flame of a candle quickly, and the end which is in this will 
not take fire, but only the wood a little way from it, in the burn- 
ing part of the flame ; so, also, if you hold a little splinter of wood 




GAS-MAKING AND GAS-BUENING. 



75 



Description of the flame of a candle. 



directly* across the flame, so that it shall run through the dark 

part, there will be a little in the middle that is not burned at all, 

while each side of this the splinter will take fire. 

There are really three parts in the flame, as represented in Fig. 
32, the burning shell being composed of two 
parts. The outer part of the shell, 1, is not 
as bright as the inner part, 2. As the gas, 3, 
rises from the melted tallow, some of it con- 
tinually passes into the shell, 2, where the hy- 
drogen burns very briskly, and sets on fire 
the fine particles of carbon. It is these par- 
ticles, thus lighted and beginning to burn, 
that make that part of the flame so bright. 
As they pass into the outer part of the flame, 
1, their burning is finished by a perfect union 
with oxygen, forming carbonic acid. In mak- 
ing this union they are not as bright as 
when the burning hydrogen first sets them 
on fire. 

It is these same particles of carbon that, 
in their burning, give the brightness to the 
flame of illuminating gas, as already stated 
on page 65. We have the same thing in the 
flame of burning fluid, as it is called. This 
fluid is a mixture of alcohol and oil of tur- 
pentine. Alcohol burns with a pale flame, 
as you have often seen in spirit lamps ; it is 

because there is not much carbon in it. But add to it oil of tur- 




76 



GAS-MAKING AND GAS-BUKNING. 



Gas made in a tobacco-pipe. 



Gas-works. 



pentine, and then you have a bright light, because there is a plen- 
ty of carbon in the turpentine. 

You will want to know how they make gas to distribute in 
towns and cities. It is made generally from coal. You can make 
gas yourself, in a very simple way, with a tobacco-pipe, as seen in 

Fig. 33. The bowl 
of the pipe is filled 
with pieces of bitu- 
minous coal about 
the size of peas, and 
then it is closed 
tight with a layer 
of clay. The bowl 
of the pipe is then 
placed in the fire, as 
you see. In a short 
time smoke issues 
from the stem of 
the pipe. This is 
gas ; and if you set 
fire to it a good light will be produced. 

Yery much in this way is the gas made at the gas-works. 
Large iron vessels, or retorts, are used, inclosed in furnaces. Into 
these retorts coal is put, and the heat drives off the gas. It is 
impure as it comes off, and must therefore be purified before it is 
sent off in the distributing pipes. When it comes to us, there- 
fore, in our houses, it is clear, and not like the smoke which comes 
out of the tobacco-pipe. 




GAS-MAKING AND GAS-BURNING. 77 

Explosions of burning gases. Experiments. 

I have spoken now and then of explosions taking place with 
gases. Now what is such an explosion ? What takes place ? It 
is a sudden burning of considerable gas at once, and the gas that 
thus burns unites with oxygen in the burning. Thus, if we mix 
together oxygen and hydrogen, and then set fire to the mixture, 
there is an explosion. The whole of the hydrogen burns at once 
in the oxygen, and in the burning water is formed, just as when 
hydrogen is quietly burned as it comes out of a tube. When 
coal gas, escaping from a leak, explodes on bringing a light to it, 
the explosion is produced by the sudden union of the gas with 
the oxygen of the air. 

You can explode mixtures of oxygen and hydrogen safely in 
many ways ; I will mention two. 

Introduce into a strong soda-water bottle, by means of the pneu- 
matic cistern, hydrogen g&s enough to occupy two thirds of the 
bottle ; let in now oxygen gas enough to fill it ; cork the bottle, 
and take it out of the cistern ; wrap a thick towel around it, and, 
holding it in your hand, draw the cork, and apply a light to the 
mouth of the bottle. A loud explosion occurs, and water, formed 
by the union of the gases, bedews the inside of the bottle. The 
towel is used so that, if the bottle should happen to break, the 
broken glass will not cut the hand. 

In Fig. 34, on the following page, I show you a beautiful way 
of exploding these gases. The man holds an air-tight bag filled 
with the mixture of oxygen and hydrogen above spoken of, and 
he has a tobacco-pipe in the mouth of the bag. In this mouth is 
a stop-cock, so that he can let out the gas as he pleases. Putting 
now the bowl of the pipe in some soap and water, he lets out some 



78 



GAS-MAKING AND GAS-BUKNING. 



Bursting bubbles. 



Burning oxygen and hydrogen together. 



Fig. 34. 




of the gas, and so forms a bubble. Now, as hydrogen is so very 
light, and two thirds of the gas in the bubble is hydrogen, the 
bubble flies off upward. As it flies the lad touches it with a 
light, and it explodes. In trying this experiment caution is nec- 
essary, lest the light be brought near the bowl of the pipe, and 
thus explode all the gas in the bag. 

If we let a small stream of oxygen gas and another of hydro- 
gen burn together, the most intense heat is produced. It will 
melt and burn up the hardest substances. In Fig. 35 you see 
represented an arrangement for burning these two gases together. 
The oxygen is in the bag, with a weight upon it to make the gas 
pass out through the pipe. The end of the pipe is brought close 
to the flame of the hydrogen, which comes up from a bottle which 
you see below. 



GAS-MAKING AND GAS-BURNING. 



79 



Oxyhydrogen blow-pipe of Dr. Hare. 



Fig. 35. 




The chemist commonly has two gas-holders, as they are called, 
containing the two gases. From these go two tubes, which join 
together in one jet. Such an arrangement is called the oxyhy- 
drogen blow-pipe, and was invented by Dr. Hare, of Philadelphia. 

If you hold with a pair of pliers a piece of very small copper 
wire in the burning jet of these two gases, it will burn with a 
beautiful green fllame. If you use iron wire, the bright sparks will 
fly merrily. In neither case is a mite of the oxygen or hydrogen 
lost ; the oxygen unites, in this intense heat, with the hydrogen 
to form water, and with the metals to form oxyds. Iron rust, or 
oxyd of iron, is formed with the iron, and oxyd of copper with the 
copper. Platinum, the heavy metal mentioned in the beginning 
of Chapter IX., can not be melted in the hottest furnace, but it 
melts readily in the flame of oxygen and hydrogen. 



80 GAS-MAKING AND GAS-BURNING. 

Drummond light. 

You have perhaps heard of the Drummond light. It is made 
by causing the oxyhydrogen flame to strike against a piece of 
lime. The light produced has the dazzling brightness of the sun. 
It receives its name from its discoverer, Lieutenant Drummond, 
of the English navy. It is of great use for many purposes. It 
can be seen farther at sea than any other light, and it is used, 
therefore, very much for signals at night. 

There is one singular fact about this lime light. Though the 
heat produced is so intense, the lime is not in the least changed. 
The oxygen and hydrogen only are changed ; these unite to form 
water, which flies off in the air. 

Questions. — What is said of gas factories ? What two substances are in tallow ? 
Describe the melting of the tallow as the candle burns. Why does the melted tal- 
low go up the wick ? Explain capillary attraction. What is the gas made from the 
melted tallow ? Describe the flame of the candle. How can you prove that the 
dark inner part of the flame is gas which is not yet on fire ? Give the experiment 
with the match. Give that with the splinter of wood. Explain Fig. 32. What is 
said of illuminating gas ? What of burning fluid ? Describe the making of gas as 
represented in Fig. 33. Describe the making of it at the gas-works. What is said 
of explosions of gases ? Describe the experiment with the soda-bottle. Describe 
the experiment represented in Fig. 34. Describe the arrangement in Fig. 35. What 
is the oxyhydrogen blow-pipe ? Tell about the burning of copper and iron in the 
flame of the two gases. What are the substances formed in burning them ? What 
is said of platinum? What is the Drummond light? Of what use is it? What 
fact is stated about it ? 



STRIKING FIRE. 81 



The spark in striking fire burning iron. 



CHAPTER XII. 

STRIKING FIRE. 

Every body has seen fire struck from the heel as it hits upon 
a stone, and yet how few know exactly what it is that is done. 
They see the spark, and are satisfied with saying of the phenome- 
non that it is striking fire, as it is expressed. 

But what is the spark? It is something more than a mere 
show of light; it is a burning substance. What is this substance? 
It is a bit of steel or iron from a nail in the heel ; this is knocked 
off as the heel strikes the stone, and there is heat enough made 
by the blow to set it on fire. 

The spark, then, is a particle of burning iron. But how does 
it burn? Precisely as the steel burned in the jar of oxygen gas 
in the experiment noticed on page 21. There is oxygen in the 
air, and the blow of the heel upon the stone makes the bit of iron 
so hot as to cause the oxygen of the air to unite with it at once ; 
and they unite so quickly that they light up in doing it, and so 
the little mite of iron flies off a bright spark. 

The spark falls and goes out. It is so small that you can not 
find it. But what is it? Is it iron ? No, for it has been burned. 
And what is it to burn iron ? It is to make oxygen unite with 
it. The fallen spark, then, is not iron, but iron and oxygen united 
together, that is, an oxyd of iron. 

Now suppose that the air were all oxygen, instead of being ox- 
ygen and nitrogen mixed together. Your striking fire would not 

F 



82 STRIKING FIRE. 



The tinder-box. Keeping fire in old times. 

end in a little spark ; there would be a shower of sparks. And 
then, too, the nail itself would get to burning, like the steel wire 
in the jar of oxygen. Indeed, the fire, fed by the oxygen, might 
go on to burn the shoe, and your clothes, and your flesh, unless 
water were applied to shut out the oxygen. 

Before Lucifer matches were invented, every family was in pos- 
session of a tinder-box for the purpose of striking a light. The 
apparatus consisted of a piece of steel, a flint, some half-burnt rags 
in a tin box, and some matches, which were splinters of wood with 
a little sulphur on their ends. The way in which a light was ob- 
tained was this : The flint was struck upon the steel held over the 
tinder till the tinder was set on fire by a spark from the steel ; 
then, applying a match to the fired tinder, the sulphur on its end 
took fire. It often was necessary to work some time to get a 
light in this way. I remember having my patience sorely tried 
by this operation many a time when I was a student in college. 

In those times the common fuel was wood, and great pains 
were taken by families to preserve fire by covering up coals in 
ashes. This was always done over-night, and, in the summer, com- 
monly during a portion of the day. If the coals happened to go 
out, people often preferred going to a neighbor's house for live 
coals to working over the tinder-box. 

The invention of Lucifer matches, by which we can produce a 
light in a moment, has put aside all the tinder-boxes. That you 
may see what kind of an apparatus was formerly used for setting 
fires and lights agoing, I give you, in Fig. 36, a picture of quite 
a complete apparatus. B is the flint, C the steel, and A the tin- * 
der-box, with a candle fixed in its cover. In the lower part of the 



STRIKING FIRE. 



83 



Tinder-box described. 



Indian mode of getting fire. 



Fig. 36. picture you see D, the 

bundle of matches, and 
E, the tinder-box open- 
ed. You observe an in- 
side cover to the box : 
this is for the purpose 
of putting out the tin- 
der after the match has 
been lighted from it. 
This was put in upon 
the tinder, pressing it 
down ; then the steel 
and flint were put in 
upon this cover, so 
that the whole appara- 
tus was very snugly 
packed. 

The method which the savage formerly adopted for obtaining 
fire was more laborious than that of the tinder-box. He sharp- 
ened a piece of hard wood to a point, and very rapidly turned 
this, after the manner of a drill, against a soft piece of wood, hav- 
ing some light chips around it. It required great practice to en- 
able one to move the pointed stick with sufficient rapidity to set 
fire to the chips. Any one can make two sticks quite warm by 
rubbing them together, but to make them hot enough to set any 
thing on fire is a different matter. The Indian, therefore, must 
have thought the tinder-box a wonderful invention when he came 
to see the white man use it. 




84 STRIKING FIRE. 



Lucifer matches. Oxygen in them. Machinery taking fire by friction. 

In all these cases the fire is produced in the same way. It is 
the union of the oxygen of the air with the wood of the Indian, 
with the steel of the tinder apparatus, and with th& phosphorus 
of the Lucifer match that makes the fire ; and it is heat in each 
case that causes the union. The match takes fire the easiest, be- 
cause but little heat is required to make the phosphorus unite 
with the oxygen. You can produce enough heat for this by a 
slight rubbing. It is supposed by some that many of our fires 
are occasioned by matches carelessly left about. A cat or a rat 
might knock them off from a shelf, and, in doing so, might rub 
the ends sufficiently to set fire to them ; and, if they should hap- 
pen to fall upon something combustible, as paper or clothing, a 
fire might result. Matches ought always to be kept securely shut 
up in boxes. 

What you see on the end of a match is not phosphorus alone, 
but a mixture of this with some other substances, which make it 
burn more readily than if it were alone. The reason is that they 
have considerable oxygen in them. You see how this is. The 
more oxygen there is to unite with the phosphorus, the more 
lively will it burn ; and, in the lighting of the match, the friction 
makes the phosphorus unite with the oxygen in these substances, 
in addition to that which is in the air. 

Machinery is sometimes set on fire by the heat occasioned by 
friction ; that is, the iron part of it becomes so hot that it heats 
the wood part sufficiently to make the oxygen of the air unite 
with it. If the axles of railway cars are not kept well oiled, the 
heat produced by the friction sets the little oil that is in the axle- 
boxes on fire ; that is, makes the oxygen of the air unite with it. 



STRIKING FIRE. 



85 



Knife-grinding. 



Perkins's machine. 



The knife-grinder, as he, with his rapidly revolving wheel or 

disk of stone, makes sparks fly 
off, really burns up a part of 
the knife that he is grinding. 
In Fig. 37 is represented a ma- 
chine invented by the late Ja- 
cob Perkins, by which steel 
is burned up in considerable 
quantity. A disk of soft iron 
is made to revolve at the rate 
of 5000 times a jninute. If a 
hard file be held against the 
edge of this disk, the rapid fric- 
tion will burn up that part of 
the file which touches the disk, 
and a shower of sparks will 
be thrown upward. Here you 
have the same effect produced 
as when you strike fire with your heel. It is the union of the 
oxygen with particles of the file that makes the sparks. 

Questions. — In striking fire, is the spark merely light? What is it? Give the 
comparison between this and the burning of iron in a jar of oxygen gas. What is 
the spark after it has fallen and gone out? What would come of this striking fire 
if the air were all oxygen ? What is said of the old-fashioned tinder-box ? What 
of the pains to preserve fire before Lucifer matches were invented ? Describe the 
apparatus of the tinder-box, as represented in Fig. 36. What is said of the Indian's 
mode of obtaining fire ? What makes the fire in all the cases mentioned ? What is 
said of accidental fires by matches? What of the substance on the ends of match- 
es ? What of setting machinery on fire? What of setting oil on fire in axle-box- 
es ? Tell about the knife-grinder. Explain Fig. 37, 




86 AJSTIMAL HEAT. 



Heat of our bodies produced by combustion. This compared to the burning of a candle. 



CHAPTER XIII. 

ANIMAL HEAT. 

What is it that makes your body warm ? Clothes and fires, 
you will perhaps say. No ; they help to keep you warm, but they 
do not make you so. The heat that makes you warm is produced 
in your own body, and clothes and fires only serve to keep the 
warmth in a§;er it is made. The heat in you is made by a real 
combustion. There is a fire going on every where in your body. 
It is a real fire, though there is no flame nor light. 

This is one reason that you can not live without oxygen. This 
gas is needed to keep up the fire that is in your body, just as it 
is needed to keep all the fires and lights burning. 

The burning in your body is like the burning of a common 
candle in the results of the combustion. The oxygen of the air 
unites, as you learned on page 60, with the carbon of the candle 
to form carbonic acid, and it unites with the hydrogen of the can- 
dle to form water. So, also, the oxygen that goes into your lungs 
and enters the blood, unites with the carbon of your body to form 
carbonic acid, and with its hydrogen to form water. 

But where in the body does the oxygen find the carbon and 
the hydrogen? It finds them every where. They make up, in 
part, the very substances of your body, as they do the substance 
of the candle. The blood circulates every where, to the very 
ends of your fingers, and it carries in it the oxygen that it takes 



ANIMAL HEAT. 87 



Where the fire in our bodies is. A comparison and a difference. 

from the air which comes into your lungs. And the warmth in 
your fingers, as well as every where else, is made by the union 
of the oxygen with the hydrogen and the carbon that are there. 

But you will ask, " Are carbonic acid gas and water formed in 
the very ends of my fingers as they are in the burning candle?" 
Exactly so. "What becomes of them?" you will ask again. 
"Do they go off from my fingers into the air as they do from 
the candle?" Perhaps some of the water does. "But the car- 
bonic acid gas, what becomes of that?" It goes in the blood to 
your lungs, and there is breathed out into the air. 

The breathing out of carbonic acid gas I have already told you 
about in Chapter VIII. This gas that you breathe out comes, 
then, from all parts of the body. It is rather an amusing idea, . 
that when you breathe into lime-water and make chalk, a part 
of the gas that you make it with came from the very ends of 
your fingers and toes, and was made there by a sort of fire. 

Some of the water, too, that is formed by this fire in your body 
goes out in your breath ; and it goes out in vapor, just as it goes 
up from a burning candle. This vapor will collect on a cold glass 
as you breathe on it, as you can collect the vapor from a candle 
by a glass jar put over it, as represented on page 11. 

The candle burns up ; so does your body. The fire consumes 
some of your body every where all the time. But there is one 
great difference between your body and the candle in this matter. 
The candle is soon all gone, for there is no making up for what 
is consumed. But your body remains about the same day after 
day, although some of it is burning up all the while. The reason 
is that there is in the body a constant supply of new substance in 



88 ANIMAL HEAT. 



Some of our food fuel for the fire that burns in us. 



place of that which is burned. Your body, then, is more like a 
lamp fed by a fountain of oil than like a candle. 

A part of the food that we eat is fuel to keep up the fire in us ; 
that is, it goes to supply the carbon and hydrogen that are con- 
tinually burned up in our bodies. There are some kinds of food 
that furnish a great deal of carbon and hydrogen, and so are of 
great use in keeping up the fire in us. Sugar is one of these ; 
fat is another. Inhabitants of very cold climates, as the Esqui- 
maux, eat large quantities of fat meat and oil, because they are 
of use in keeping them warm. They need food that has a great 
deal of charcoal in it for fuel, so that a good fire may be kept up 
in them to guard against the extreme cold of the climate. They 
love food of this kind very much. A captain of a vessel once in- 
vited one of these people to dine with him. His guest declined 
to take the coffee and wine which were offered him, but, seeing an 
oil-can near by, he took it up and drank down all the oil. That 
was a drink that he had learned to like, for he had always been 
used to drink it to keep himself warm. But the coffee and wine 
he did not think of much account. 

I have spoken of sugar as being one of the kinds of food that 
furnish fuel for the fire in us. You can hardly believe that a 
large portion of sugar is charcoal, but so it is. Indeed, sugar and 
wood are composed of the same things, as you will learn more 
fully in another part of this book ; and as you can get charcoal 
from wood, so also can you get it from sugar. 

I have told you on page 51 that the carbonic acid which a full- 
grown man has breathed out from his lungs in a year contained 
about 200 pounds of charcoal, Now all this carbonic acid came 



ANIMAL HEAT. 89 



How exercise warms us. Our bodies heat the air around us. 

from the fire in his body, and in this fire all this 200 pounds of 
charcoal united in his body with oxygen. Where did all this 
charcoal come from ? He swallowed it in his food — in the sugar 
and fat, etc., that he has eaten. You swallow every year an 
amount of charcoal which would weigh more than you do, and 
this is burned up in you to keep you warm. 

You know that when you run or play very hard you become 
heated. Think why this is so. Your heart beats quicker than 
when you are still, and the blood flows very rapidly in your ar- 
teries and veins. At the same time, you breathe quick. Now 
the quick breathing makes more air, and therefore more oxygen, 
go into the lungs ; more oxygen, of course, gets into the blood, 
and, as the circulation is quickened, the oxygen is carried every 
where more rapidly. The fire must therefore burn more briskly 
in every part of the body, for the same reason that you make a 
fire in the fireplace burn better by blowing it. The oxygen in 
both cases, in the fire in the body as well as that in the fireplace, 
comes faster to the carbon and hydrogen. 

Did you ever think that your body is always giving out heat 
to the air around you? The air is almost always cooler than 
your body, even in very hot weather. You are uncomfortably 
warm in a hot day, not because the heat of the air goes into your 
body, but because your body does not give off enough heat to the 
air. Once in a very great while there may come a day when the 
air is as hot as your body, and then your body does not give out 
heat ; but, with this exception, the air is always taking heat from 
you, even when you are sitting by a very warm fire. 

A great many persons, therefore, crowded together, give out a 



90 . ANIMAL HEAT. 



The heat produced in crowded rooms. The use of clothing. 

great quantity of heat. We see this often illustrated in large par- 
ties. The rooms are comfortable at first, when only a few persons 
are gathered, but when the rooms are crowded the air is uncom- 
fortably warm. This is because there is so much of carbon and 
hydrogen united with oxygen in all these persons. If a hundred 
persons are present, we may think of them as a hundred fires 
warming the air. 

If you stand out in the cold without sufficient clothing, you be- 
come chilled. Observe just how this is: the air is all the time 
passing into your lungs, carrying in the oxygen, which keeps the 
fire in you burning; but the fire is not sufficient to keep you 
warm, because the cold air is taking away heat so fast from all 
the outside of your body. 

How can you remedy the difficulty? In two ways. One is 
to make the fire in you burn more briskly ; this you can do by 
exercising in some way — running, jumping, working. This will 
make your blood circulate quicker, and you will breathe faster, so 
that more oxygen will go into the blood, and brighten up the fire. 
You have seen teamsters in cold weather strike their arms across 
the body, letting the hands come over upon the back. This is to 
make the blood go more freely to the very ends of the fingers, 
that there may be an abundance of oxygen there to unite with 
the carbon and hydrogen, and so produce sufficient warmth. 

Another way to remedy the difficulty is to put on more cloth- 
ing. The object of this is to keep in the heat which the fire in 
you is constantly making. You see very readily the reason that 
you need more clothing when you are riding in the cold than 
when you are walking or playing. The fire is not as brisk when 



ANIMAL HEAT. 91 



Difference in the coverings of animals in cold and hot climates. 



you are still as when you are exercising, and so you need to take 
more pains to keep the heat from escaping into the air. 

Animals that live in cold climates have clothing provided for 
them by the Creator which is fitted to keep in the heat which is 
made in their bodies ; they are clothed with furs for this purpose. 
Contrast the polar bear and the elephant in this respect. The 
bear has a good furry coat, while the elephant, that lives in a 
warm climate, has only a few straggling hairs upon his skin. 

Questions. — What makes the heat in your body? What is said about not being 
able to live without oxygen ? Give the comparison between the combustion in your 
body and that of a candle. What does the oxygen that goes into your lungs unite 
with to produce heat ? Where does it go to find the substances with which it unites ? 
How do the water and the carbonic acid formed in the combustion of the body es- 
cape into the air ? Give the comparison between the candle and your body in rela- 
tion to the vapor produced by this combustion. Show the difference between the 
body and the candle as to being consumed. What is said of food as being fuel ? 
Tell about the Esquimaux. Relate the anecdote of the Captain's guest. What is 
said of the amount of charcoal that we eat in our food ? Explain why you become 
so much heated on exercising briskly. What is said about our giving out heat to the 
air? What about many people being together? Why are you chilled when stand- 
ing in the cold without sufficient clothing ? What is the first way mentioned of get- 
ting rid of the difficulty ? What other way is mentioned ? Why do you need more 
clothing in riding than in walking in the cold ? What is said about animals living 
in cold climates ? 



92 IRON-RUST, POTASH, SODA, AND LIME. 

Oxygen added to iron in the process of rusting. 



CHAPTER XIV. 

IRON-RUST, POTASH, SODA, AND LIME. 

I HAVE told you that, when iron becomes rusted, it is a sort of 
burning or combustion that does it. Oxygen unites with the iron 
as it does with charcoal when that is burned. There is no light 
made, because the combustion is so slow. But when we rust iron 
quickly, that is, when we burn it in oxygen gas, there is a plenty 
of light. 

Which do you think is the heaviest — a slip of iron, or the same 
after it is rusted ? The iron, you will perhaps say. Why ? Be- 
cause the rust eats it, says one. And, says another, people always 
say of a stove-pipe, when the rust has made holes in it, that it is 
rusted away. But let us look at this. When iron rusts, oxygen 
is added to it or is united with it. Of course, it will weigh more 
with this addition. To be sure, oxygen is a very light substance, 
nearly as light as air. But it has some weight, and this weight is 
added to the iron when the iron turns to rust ; and it is to be re- 
membered that, a very considerable bulk of oxygen is added. It 
takes a great deal of oxygen to make but a little rust. When- 
ever you see rust, then, you can think of a large quantity of this 
gas as being condensed into a very little space as it is united with 
the iron ; and, thus united, it is no longer a gas, but a part of a 
solid substance. 

But in what we commonly call rust there is something besides 
the oxygen united with the iron : there is water in it. It does 



IRON-RUST, POTASH, SODA, AND LIME. 93 

Amount of water and oxygen in iron-rust. No affinity between gold and oxygen. 

not show itself as water, for the rust is dry. How is this ? The 
water in the rust is not a liquid now, just as the oxygen in it is 
not a gas. Both the liquid and the gas are now parts of a solid 
substance. 

You will be surprised when I tell you how much of oxygen 
and water there is in iron-rust. In two pounds of rust there is 
nearly half a pound of oxygen and about the same weight of wa- 
ter ; that is, there is nearly half a pint of water in the two pounds 
of rust, and about 40 gallons of oxygen gas. 

Observe the difference between iron-rust and the sparks that 
fly off when we burn iron in oxygen gas. The sparks are com- 
posed only of iron and oxygen, but the yellow rust is composed 
of iron, oxygen, and water. 

Most metals will, like iron, burn, or, in other words, will unite 
with oxygen; but there are some metals that will not burn at 
all. This is because they have no liking or affinity for oxygen. 
Gold is one. If you apply heat enough to melt it, it will not take 
any of the oxygen of the air to itself. So, also, you may have it 
gilded upon vanes, and exposed to the air year after year, and it 
will not tarnish ; that is, it will not burn or rust as iron does. Iron 
exposed to the weather in this way rusts in a very little time, un- 
less it be covered with paint to keep the oxygen of the air away 
from it. 

There are some metals that like oxygen so well that they will 
unite with it at once whenever oxygen touches them, and some- 
times will burn smartly in doing it. Potassium is one of them. 
^?his is a metal that no one has ever yet found any where. How, 
then, you will ask, do we know that there is such a metal? It 



94 IRON-BUST, POTASH, SODA, AND LIME. 

Davy's discovery of potassium. How this metal can be kept. 

was first found out by Sir Humphrey Davy, a great English 
chemist, who was once a poop boy, but became a great man be- 
cause he was always studying out things. 

I will tell you a little about his discovery. Every body is 
familiar with potash. Now, for some reasons which Davy thought 
out, he came to believe that this is not a simple substance, but a 
compound. He tried some experiments about this. He at length 
discovered that it is composed of oxygen and a metal just as iron- 
rust is. He separated the metal from the oxygen, and called it 
potassium. But the difficulty was to keep the metal after it was 
obtained. It was constantly turning into potash ; for there is oxy- 
gen every where, and the potassium and the oxygen would get 
together somehow, because they have such a liking or affinity for 
each other. You see, now, why it is that this metal is never 
found alone by itself. It is always united with oxygen or some 
other substance, as you will hereafter see. 

The only way in which this metal can be kept is to shut it up 
in a prison where it can not get at any oxygen. But it is difficult 
to find such a prison, for there is oxygen in almost every sub- 
stance in the world. It is commonly kept in naphtha, a liquid 
which happens to have no oxygen in it. With this all around it 
as a covering to keep out its great friend oxygen, it can be pre- 
served perfectly pure. 

Potassium is a bluish-white metal, quite soft, so that you can 
mould it between the fingers almost like wax when it is a little 
warm, but it is brittle when cooled down to the freezing point of.. 
water. It is a very light metal, so light that it will swim on water. 

If potassium be left exposed to the air it tarnishes at once, and 




IRON-RUST, POTASH, SODA, AND LIME. 95 

A metal that swims and takes fire on water. 

in a short time is all turned to potash, the oxygen of the air uni- 
ting with it. 

If you throw a little piece of it upon water, it steals away the 
oxygen from the hydrogen of the water, and flies Fig. 38. 
about the surface, sending up a beautiful pink flame, 
as represented in Fig. 38. This flame is the hydro- 
gen which is set free by the union of the potassium 
with the oxygen of the water. The hydrogen burns 
because this union is made quickly, and so produces heat enough 
to set fire to the hydrogen. The color is given to the flame by 
fumes of the potassium. If this metal be thrown upon ice the 
same burning will occur. The cold will not prevent the potassi- 
um from stealing away the oxygen from its companion in the ice, 
hydrogen, neither will it prevent its setting the hydrogen on fire. 

It seems very strange to us that a metal should float on w^fcer 
and burn up while it is floating. When Sir Humphrey Davy 
made the discovery he astonished every body. Even his brother 
chemists were astonished. It is related that Davy put a small 
piece of the newly-discovered metal into the hand of his friend 
Dr. Wollaston, a celebrated chemist, and Dr. Wollaston spoke of 
it as being quite heavy. Davy soon showed him his mistake by 
throwing it into water. The philosopher expected to see it sink 
like lead, and was utterly surprised to see it both float and burn. 

You have seen, in previous chapters, that phosphorus has a 
considerable liking or affinity for oxygen. It likes it so well that 
we have to keep it imprisoned in water to prevent it from join- 
ing company with the oxygen of the air. But you see that potas- 
sium likes oxygen much better than phosphorus does, for it will 



96 IRON-RUST, POTASH, SODA, AND LIME. 

Oxyds. Soda and salt. Alkalies. 

even take it away from the hydrogen in water, although the hydro- 
gen and oxygen are very strongly united together in that liquid. 

Iron-rust is an oxyd of iron. It is so called because it is oxy- 
gen and iron united together. So the iron, when rusted, is said 
to be oxydized. In like manner, potash is an oxyd of potassium. 

What is very commonly called potash is really potash united 
with carbonic acid, and of this I will tell you in another chapter. 
What the chemist calls potash, that is, the oxyd of potassium, is 
a powerful substance. It will, like the strong acids, the nitric 
and sulphuric, eat flesh, and so is callqd a caustic. 

As potash is an oxyd of potassium, so soda is an oxyd of a 
metal called sodium. This metal will swim on water like potas- 
sium. When thrown upon water it decomposes it, taking the 
CtiM&en from the hydrogen, as the potassium does. A hissing 
SOTmd is produced, but the escaping hydrogen does not burn un- 
less the water be hot. When it does burn the flame has a beau- 
tiful yellow color, which is given to it by the fumes of the metal. 

There are great quantities of this metal in the world, for it is 
one of the ingredients of common salt. But, like potassium, it is 
never found alone by itself. It is always united with oxygen or 
some other substance. 

Potash and soda are called alkalies. They have an acrid taste, 
the very opposite of that of acids. There is one substance, am- 
monia, which is called volatile alkali, because it is so ready to fly 
off into the air, volatile coming from the Latin word volo, to fly. 
Potash and soda are sometimes termed fixed alkalies, in distinc- 
tion from the ammonia, because they have no disposition to fly off, 
but stay or are fixed to the spot where they are. 



IRON-RUST, POTASH, SODA, AND LIME. 97 

« . 

Ammonia. Quick-lime and slaked lime. Mortar. 

Ammonia is a colorless gas, and is very pungent. Its compo- 
sition is very singular. It is composed of nitrogen and hydrogen. 
It forms, with carbonic acid gas, the smelling salts with which 
you are so familiar. 

Lime was supposed to be a simple substance or element before 
the discoveries of Sir Humphrey Davy. But this, like soda and 
potash, he found to be an oxyd of a metal. This metal, called 
calcium, it is very difficult to obtain, because it has so great an 
affinity for oxygen. It is hard to get calcium out of the company 
of its friend oxygen long enough to let us see it. When it is 
seen it looks like silver. United with oxygen, calcium forms 
lime, or what is commonly called quick-lime. If water be added 
to lime it is called slaked lime. Observe that word slaked. Peo- 
ple sometimes speak of slaking the thirst ; so, in the case of lime, 
there is a thirst, as we may say, for water, and the lime will take 
into itself a great deal of it. But there is a certain amount that 
it will take and no more. When it has got that amount its af- 
finity is satisfied, or its thirst is slaked. So it is called slaked 
lime. 

Lime will become slaked after a while if it be merely exposed 
to the air, for it has such an affinity for water that it will drink in 
the moisture from the air. 

In making mortar the lime is slaked ; and so great is the af- 
finity of lime and water for each other, so eager are they to unite 
together, that great commotion and heat are produced, as you 
have probably often witnessed where building is going on. 

Slaked lime is dry, and yet in every four pounds of it there is 
one pound of water. This is about the same proportion that 

Gr 



98 IRON-RUST, POTASH, SODA, AND LIME. 

Amount of "water in plastering. 

there is in iron-rust, which I told you about in the first part of 
this chapter. This water does not exist as water in the lime. It 
is no longer a fluid, but it is a part of a solid. 

One quarter of the lime in the plastering on our walls is, then, 
water. Pailful upon pailful of water is in the plastering of a 
single room ; and if the house be built of brick, what quantities of 
water are there in all its plastering and mortar! The common 
idea of people is, that when plastering and mortar dry, the water 
that is in them all passes off into the air, just as it does from a 
wet cloth when it dries. But only a part of it thus passes off, a 
large portion becoming a part of the dry solid. 

Questions. — What is said of the union of oxygen with iron ? What of the weight 
which the oxygen adds to the iron? What of the bulk of the oxygen added? What 
else besides oxygen is added to iron in rusting? In what condition is the water 
which is added ? How much water and oxygen are there in iron-rust ? What is 
the difference between iron-rust and the sparks of iron burning in oxygen gas? 
What is said of the union of other metals with oxygen? How is it with gold? 
What is said of the affinity of some metals for oxygen ? Tell about the discovery 
of the metal potassium. Why is it difficult to keep this metal ? Why is it never 
found alone by itself? In what way is it kept? Describe the metal. What hap- 
pens to it if left exposed to the air ? What happens if it be thrown upon water ? 
Explain the burning. Tell about throwing it on ice. Give the anecdote about Dr. 
Wollaston. What comparison is made between phosphorus and potassium? Ex- 
plain oxydation. Why is potash said to be caustic ? What is soda ? What is said 
of the burning of sodium on water ? In what substance does this metal exist in 
abundance in the earth ? What are alkalies ? Why is ammonia called the volatile 
alkali ? Why are potash and soda called fixed alkalies ? What is said of ammonia ? 
What is calcium ? What is quick-lime ? What is slaked lime ? What is the mean- 
ing of the word slaked ? What is said of exposing lime to the air ? What of making 
mortar ? How much water is there in slaked lime ? What is said of the quantity 
of water in mortar plastering ? 



METALS AND THEIR OXYDS. 



Weight of metals. Platinum. Mercury. Metals opaque substances. 



CHAPTER XV. 

METALS AND THEIR OXYDS. 

I have already told you about a few metals and their oxyds. 
Most of the metals unite quite readily with oxygen, but some few 
do not. I will now go on to describe those metals which are 
most important and interesting, noticing their oxyds at the same 
time. 

Most of the metals are heavy. One of them, platinum, is the 
heaviest substance in the world. But some of them, as you saw 
in the previous chapter, are so light that they will swim in water. 

All of the metals are solid but one, mercury. This is a liquid. 
You see it in thermometers. 

A metal is a simple substance, an element, and not a com- 
pound. There are nearly fifty of these metallic elements, while 
there are only about a dozen of all the other elements in the 
world. 

The metals are opaque substances ; that is, the light will not 
pass through them. Glass is transparent, and not opaque, for you 
can see through it ; but you can not see through a piece of iron 
or tin. The gases are transparent, as you learned in Chapter II. 
Water is also. You can see substances, you know, at the bottom 
of clear water in a pond or stream ; but if you have a cup of 
mercury, you can not see any thing in the bottom of the cup. 

There are some substances that you can not see through, and 
yet light can shine through them. They are said to be translucent 



100 



METALS AND THEIR OXYDS. 



Properties of metals. 



Variety of the uses of iron. 



Metals are neither transparent nor translucent. When gold is 
made into very thin leaf by hammering, it is translucent ; but, 
however thin it may be made, it is never transparent. 

Metals have a certain brilliancy which is called the metallic 
lustre. Some of them can be polished very highly. 

There are certain properties which belong to some of the metals 
which make them very valuable to man. There is malleability. 
This word comes from the Latin word for hammer, malleus. Gold 
is very malleable ; that is, it can be hammered out into very thin 
leaves. Silver, lead, and tin are also very malleable, though not 
as much so as gold. Iron is considerably so when it is heated. 
Then there is ductility, the property by which some metals, as gold, 
silver, and iron, can be drawn out in the shape of wire. 

Iron is the most valuable and abundant of all the metals, and 
it is put to the greatest variety of uses. It is on account of these 
uses that the Creator has provided so much of it for man in every 
part of the world. Here is a piece of poetry in which some of the 
many uses to which this metal is put are mentioned : 



" Iron vessels cross the ocean, 
Iron engines give them motion : 
Iron needles westward veering, 
Iron tillers vessels steering ; 
Iron pipe our gas delivers, 
Iron bridges span our rivers ; 
Iron pens are used for writing, 
Iron ink our thoughts inditing ; 
Iron stoves for cooking victuals, 
Iron ovens, pots, and kettles ; 
Iron horses draw our loads, 
Iron rails compose our roads ; 



Iron anchors hold in sands, 

Iron bolts, and rods, and bands ; 

Iron houses, iron walls, 

Iron cannon, iron balls ; 

Iron axes, knives, and chains, 

Iron augers, saws, and planes ; 

Iron globules in our blood, 

Iron particles in food ; 

Iron lightning-rods on spires, 

Iron telegraphic wires ; 

Iron hammers, nails, and screws, 

Iron every thing we use.'' 



METALS AND THEIR OXYDS. 101 

Iron never found pure. Difference between cast and wrought iron. 

You can think of many other uses to which iron is put besides 
those just mentioned. I think of a few just at this moment — 
pokers ; shovels ; sinks ; watch-springs ; hoops for casks, hogs- 
heads, women's skirts, etc. 

Iron is never found pure, but is always combined with oxygen, 
carbon, sulphur, flint, lime, etc. It is sometimes united with one 
of these, sometimes with several of them. When the chemist ob- 
tains it pure, it is almost white and quite soft. The iron that we 
use is obtained from iron ores, as they are termed. In these ores 
the iron is united with the various substances that I have men- 
tioned. The iron is freed from these by being heated in furnaces, 
some other things being mingled with the ore. The explanation 
of the operation you can not well understand, and I shall reserve 
it for my book on chemistry that will come after this. The iron 
obtained by it is more or less impure. The very best iron that 
can be bought has some carbon and flint in it. 

There is a great difference between cast iron and wrought iron. 
Cast iron, you know, is very brittle, while wrought iron is not. 
The difference in composition is this : In every hundred pounds 
of cast iron there are from three to five pounds of carbon, while 
there is only from one quarter to half a pound in every hundred 
pounds of wrought iron. But this is not all — the structure, or 
putting together, is very different in these two kinds of iron. If 
you observe the broken edge of cast iron, you will see that the 
iron is in little grains ; the structure, therefore, is said to be 
granular. ,But wrought iron seems to be composed of threads or 
fibres of the metal lying alongside of each other ; so it is said to 
have & fibrous structure. 



102 METALS AND THEIR OXYDS. 

Different uses of wrought and cast iron. Composition of steel. 

These two kinds of iron are used for different purposes. Pots 
and kettles are made of cast iron ; but it would not do to have 
any thing made of this which is to be continually knocked against 
hard things. If, for example, horse-shoes were to be made of cast 
iron, they would be broken by the first stone upon which they 
should strike ; they are therefore made of wrought iron. For the 
same reason, the nails with which they are fastened to the hoof are 
made of wrought iron, while common nails are made of cast iron. 

Wrought iron can be welded, but cast iron can not be. In this 
welding, which can be done only when the iron is red hot, the 
hammering unites the fibres in the two pieces together. You can 
readily see that this can not be done with the grains of the cast 
iron. 

Cast iron is so brittle that it can not be hammered into sheets 
at all ; it is not then malleable in any degree. But wrought iron 
is considerably so ; it is also ductile. 

Steel is a kind of iron, or rather a compound of iron and car- 
bon. In every hundred pounds of steel there are from two to 
two and a half pounds of carbon. In the amount of carbon in it, 
therefore, it is half way between cast iron and wrought iron. It 
may be made from either cast or wrought iron. When it is made 
from cast iron it is done by burning out half of the carbon that is 
in the cast iron. When it is made from wrought iron, carbon is 
added by heating, for several days, the wrought iron with char- 
coal in iron boxes. 

There are two kinds of steel. One is brittle ; the other is just 
the opposite— it is very flexible. Some swords can be bent dou- 
ble without breaking, and yet will at once become straight again. 



METALS AND THEIR OXYDS. 103 

The two kinds of steel. Abundance of iron. u Fool's gold." 

The steel in ladies skirts is of this flexible kind. The difference 
between the two kinds of steel is made in this way. If steel be 
heated, and then suddenly cooled, it will be hard and brittle ; if 
it be cooled slowly, it will be soft, and it can be readily hammer- 
ed out like wrought iron. All very sharp-cutting instruments 
are made of hard steel, and therefore are easily broken, as you 
may have learned sometime by carelessly breaking your pocket- 
knife. 

I have spoken of the abundance of iron in the earth. Besides 
the ores from which iron is obtained, there is also a great deal of 
iron scattered through other substances. There are some oxyds 
of iron that abound in this way. For example, almost all black 
and green stones get their color from an oxyd of iron that is in 
them. The yellow stains which we sometimes see in marble and 
other stones come from an oxyd of iron, which, by exposure to 
the air, has become iron-rust ; that is, an oxyd of iron containing 
considerable water, as you learned in the previous chapter. There 
is iron-rust in all soils, but in some there is a great amount of it, 
giving them a yellow or yellowish-brown color. 

There is one ore of iron which is often found in the form of 
beautiful crystals ; and as it has a color somewhat like gold, it has 
often been supposed to be gold by people that do not understand 
such matters; it is, therefore, called " fools' gold." People some- 
times bring some of this ore to chemists, supposing it to be some 
of the precious metal, and expecting to make a fortune, perhaps, 
from what they shall gather from their land. They are very 
much disappointed to learn that their gold is nothing but sul- 
phur and iron united together. 



104 METALS AND THEIR OXYDS. 

Iron mountains of Missouri. 

There is a great deal of iron in various parts of the United 
States. You have heard, perhaps, of the two iron mountains in 
the State of Missouri. They are ninety miles south of St. Louis. 
One of them is three hundred feet high, and the other seven hund- 
red, which makes a considerably high mountain. The ore of 
which they are mostly composed is an oxyd of iron. In every 
one hundred pounds of the ore there are seventy of iron and 
thirty of oxygen ; but there are some impurities mingled with 
the ore. These mountains are made up of lumps of all sizes, 
from that of a pigeon's egg to a middle-sized church. 

Questions. — What is said of the weight of the metals ? How does mercury differ 
from the other metals? How many metals are there? What is meant by the 
opacity of metals ? When is a substance said to be translucent ? What is said of 
gold leaf? What of the lustre of metals? What is malleability? What metals 
are malleable ? What is ductility ? What metals are very ductile ? What is said 
of the uses of iron ? What sort of substance is it when it is pure ? In what state is 
it found ? How is it freed from what it is united with ? How do wrought iron and 
cast iron differ ? What is the difference in composition ? Why is cast iron said to 
be granular ? What is the structure of wrought iron ? What are the different pur- 
poses to which these two kinds of iron are suited ? What is said of welding iron ? 
What of the malleability of iron ? What is steel ? How is it made ? What are the 
two kinds of steel ? How is the difference between them made ? For what different 
purposes are they used ? What is said of the presence of oxyds of iron in different 
substances ? What is said of " fools' gold ?" Tell about the iron mountains. 



METALS AND THEIR OXYDS. 105 

Lead compared with iron. Galena. Illustration of chemical affinity. 



CHAPTEE XVI. 

METALS AND their oxyds — Continued. 

Lead is the metal which is next to iron in abundance. Its 
color, as you know, is a bluish-gray. It is very malleable. Com- 
pared with iron, it is a very weak metal. A lead wire would not 
hold up much of a weight. This metal is therefore said to have 
but little tenacity. This word comes from the Latin word teneo, 
to hold, and means the power of holding together. It would re- 
quire a heavy weight to break an iron wire, but a small weight 
would break a lead one of the same size. Lead, therefore, is little 
tenacious, while iron is much so. 

There are three oxyds of lead. One is of a yellow color, and 
is called litharge. Another is the red oxyd, which is used in 
painting to give a scarlet color. Then there is another oxyd, 
which is of a dark brown color. The difference in these oxyds 
comes from the different proportions of oxygen in them. 

The most common ore of lead is galena, as it is called. This 
is sulphur and lead united, and is called by the chemist a sulphuret 
of lead, as fool's gold is a sulphuret of iron. It is found in crys- 
tals of a color very much like lead itself. 

There is one way of obtaining the metal from the sulphuret 
which illustrates very prettily chemical affinity. The sulphuret 
of lead is heated with iron. Now sulphur likes iron better than 
it does lead, and so leaves the lead and unites with the iron. 

The uses of lead are extensive and various. Lead pipes are 



106 METALS AND THEIR OXYDS. 

Uses of lead. Tinware. Pins coated with tin. 

used for various purposes. Then we have lead used in the form 
of sheets. It is mixed also with other metals. Thus type metal 
and pewter are composed in part of lead. Bullets and shot are 
made of lead. I have described the manufacture of shot in the 
Third Part of the Child's Book of Nature, Chapter XVIII. The 
oxyds of lead, also, are greatly used ; and, besides these, I shall 
tell you in another part of this book about some valuable sub- 
stances made by the union of lead with some acids. 

Extensive lead-mines have been found in many different coun- 
tries in all quarters of the globe. There are some very extensive 
ones in this country, especially at the West, in Missouri, Wiscon- 
sin, Iowa, and Illinois. 

Tin is a bright white metal, very soft and malleable. It does 
not tarnish easily ; that is, it does not readily rust or gather oxy- 
gen from the air. Tinware, therefore, as you know, easily keeps 
bright. This tinware is not all tin. There is really more of 
iron than tin in it. It is sheet iron coated with tin. In making 
it, thin sheets of iron are dipped into melted tin. Common pins 
are made of brass, but are whitened by having a very thin coat- 
ing of tin put upon them. This is done by boiling them in a so- 
lution of cream of tartar having in it some bits of tin. The 
cream of tartar, if you have ever taken it as a medicine, you know 
is quite acid. This acid dissolves some of the tin, and then the 
pins take away some of the tin from the acid, and so become 
coated. 

There are tin-mines in various parts of the world. The most 
famous are those of Cornwall, in England. There is little of this 
metal found in this country. 



METALS AND THEIR OXYDS. 107 

Properties and uses of copper. Uses of zinc. 

Copper is a metal of a red color. It is quite malleable, so that 
it is readily made into sheets, in which form it is much used, as, 
for example, in sheathing vessels. It does not tarnish or oxydize 
as easily as iron. If it did it would not answer to sheathe vessels 
with it. It stands heat well, and so is used for making various 
vessels for cooking purposes. Lead would not answer for such 
uses, because it melts so easily. Copper is very ductile, and there- 
fore is much used in the form of wire. It has considerable tenac- 
ity, as you may know by the strength of the wire. It is not so 
tenacious, however, as iron, for its wire will not hold up so heavy 
a weight as iron wire of the same size can. 

Copper forms a sulphuret with sulphur, and this is the most 
common ore of this metal. This sulphuret is united often with 
the sulphuret of iron. Tin and lead are very seldom found any 
where pure, that is, free from oxygen, sulphur, etc. But it is not 
so with copper ; this is sometimes found pure in large quantities. 
There is, in Washington, one mass, brought from near Lake Su- 
perior, that weighs over 3000 pounds. There are four oxyds of 
copper, of different colors. The sulphuret is very much like the 
sulphuret of iron, fools' gold, but has a deeper yellow color. 

Zinc is a bluish-white metal. It is used chiefly in the form of 
sheets for covering roofs, lining refrigerators, sinks, etc., protect- 
ing the floor or carpet from the heat of stoves, and in various 
other ways. Not long ago it was hardly used at all except for 
making brass and what is called pinchbeck. But some one, in 
experimenting with it, found that, on heating it to a particular 
degree of temperature, it could be rolled very easily into sheets. 
If heated above this degree or below it, the metal is brittle and 



108 METALS AND THEIR OXYDS. 

Zinc and iron contrasted. Antimony. Bismuth. Aluminum. Manganese. 

can not be worked at all. The heat must be managed just right 
to make it work. This discovery shows how much good a little 
experimenting will do. As soon as the discovery was made, zinc, 
which was before of little use, became extensively useful for a 
great variety of purposes. 

Zinc tarnishes or oxydizes very readily in the air. This you 
may see in the whitish coating which gathers on it. But observe 
the difference between this and the rusting of iron. When the 
zinc becomes once coated with this very thin rust, as we may call 
it, it protects the zinc from any farther action of the oxygen of the 
air ; but iron rusts in and in — there is no stopping it. If zinc did 
so it would make very poor roofing. 

Antimony is a bluish-white metal. It is found, like lead, united 
with sulphur as a sulphuret. Its principal use is in connection 
with other metals in mixtures or alloys, as they are called. It is 
often used in the composition of type-metal. The medicine called 
tartar emetic has the metal antimony in it, united with an acid. 

Bismuth is a brittle metal of a reddish- white color. It forms a 
part of some of the alloys. 

Aluminum is a bluish- white metal which exists extensively 
in the world, but it is always united with other substances. It 
is in alum, and this gives it its name. It is in all clay, and the 
chemist obtains it from this substance. 

Manganese is a gray brittle metal. It is known chiefly from 
the usefulness of one of its oxyds. This black oxyd is used to 
give a violet color to glass. The chemist uses this oxyd in ob- 
taining oxygen, as it contains a considerable amount of this gas 
not very strongly united to the metal. 



METALS AND THEIR OXYDS. 109 

Mercury. Discovery of this metal in Mexico. Silver and gold. 

Mercury is the only metal which is commonly liquid. This is 
a white metal, having a brilliant metallic lustre. It becomes solid 
in the extreme cold weather of the Arctic regions. Therefore, 
when Dr. Kane and others went to those regions, they could not 
use thermometers with mercury in them ; they were obliged to 
have thermometers containing alcohol, which was never known to 
become solid. 

This metal is sometimes found pure. It is said that the mines 
in Mexico were first discovered in this way : A hunter, as he was 
ascending a mountain, caught hold of a shrub to assist him ; the 
shrub gave way at the root, and there ran out from the ground a 
stream of mercury. It was supposed to be liquid silver, and from 
its quick movement as it runs along it has received the name of 
quicksilver. 

Most commonly this metal is obtained from the sulphuret of 
mercury, called generally cinnabar. This varies in color from 
bright red to brown-red. It is not at all like either mercury or 
sulphur. The two united together make an entirely new sub- 
stance. This cinnabar, when it is a bright red, is called ver- 
milion, and is m used, among other things, to give a red color to 
sealing-wax. 

Silver occurs in nature sometimes pure, sometimes in alloys 
or mixtures with other metals, as copper, and sometimes united 
with sulphur or some other substance. The most famous mines 
are in Mexico and South America. This metal is very malleable 
and ductile. It is not as hard as copper or as soft as gold. 

Gold is not found in nature united with other things, as most 
metals are ; it is found either pure, or mixed with some other 



110 METALS AND THEIR OXYDS. 

Platinum and iridium. The noble metals. 

metals as an alloy. It is usually alloyed with silver. It is found 
in rocks, or in sands that have worn off from rocks by the weather, 
and been washed down by the rain. 

Platinum is commonly spoken of as the heaviest of all known 
substances ; but there is another metal, iridium, found in company 
with platinum, which is a trifle heavier. Platinum is a metal 
having a color like that of steel. It is very ductile and malleable, 
like gold. No common fire can melt this metal ; it can be melt- 
ed, however, by the heat of the oxy hydrogen blowpipe, as I told 
you in Chapter XI. 

Mercury, silver, gold, and platinum have been called the noble 
metals, because they are never tarnished or oxydized by the oxy- 
gen of the air. 

Questions. — What are the characteristics of lead ? Why is it said to have little 
tenacity ? What is said of the oxyds of lead ? Tell about galena. How does one 
way of obtaining lead from galena exemplify chemical affinity ? Mention the uses 
of lead. What is said of lead-mines ? What are the qualities of tin? What is 
sheet tin, as it is called ? What is said of pins ? Where are the most noted tin- 
mines ? What are the qualities of copper and the uses to which it is put ? What is 
the most common ore of copper ? What is said about its being found pure ? How 
many oxyds of copper are there? For what is zinc used ? Whaf discovery brought 
it into extensive use ? What is said about its tarnishing ? How does it differ from 
iron in this? What is said about antimony? What of bismuth? Of aluminum? 
Of manganese ? What are the characteristics of mercury ? What is said of its 
freezing ? What of its being found pure ? What is said of cinnabar ? What of 
silver? What of gold? What of platinum ? What are the noble metals, and why 
are they so called ? 



ALLOYS AND AMALGAMS. Ill 



An alloy a mixture, not a compound. 



CHAPTER XVII. 

ALLOYS AND AMALGAMS. 

I HAVE already said something of alloys or mixtures of differ- 
ent metals. See, now, how these mixtures differ from what we 
call chemical compounds. One difference is this : When two sub- 
stances form a compound, they unite only in certain proportions ; 
but in an alloy you can mix two metals in all kinds of propor- 
tions. For example, just so much sulphur will unite with lead 
to form sulphuret of lead. This is a compound; but in the alloy 
or mixture of lead and tin you may have any proportion that you 
please. It is with alloys very much as it is with mixtures of some 
liquids. Thus you can mix alcohol or water together in any pro- 
portions that you wish. 

There is another difference. When two substances unite to- 
gether to form a compound, the substance which is formed is not, 
in its qualities, between the two that form it; an entirely new 
substance is formed, and generally wholly different from either 
of the substances of which it is composed. But see how it is with 
alloys. Brass is a mixture or alloy of copper and zinc. Its color 
is made lighter than copper by the zinc, about one quarter of it 
being of this metal. The brass is between the two metals in this, 
and also in other qualities. 

Take another case. Type-metal is made partly of lead. If it 
were wholly lead, the types would be soft, and would very soon 
wear out. There is mixed, therefore, with it some other metal 



112 ALLOYS AND AMALGAMS. 

Type-metal. Bronze. Pewter. Pinchbeck. 

to give the required hardness. Yery commonly this is copper. 
Sometimes tin is used in place of lead. This makes a better, 
though more expensive type-metal. Sometimes type-metal is 
made of zinc, copper, lead, and tin together. In the best type- 
metal there is some bismuth, which gives a good clear letter 
in printing. If you examine printed letters with a magnifying- 
glass, you will see great differences in the specimens, according 
to the kind of types used, and the length of time that they have 
been in use. You will be surprised to find how imperfect the 
letters are in their filling up in the very best of printing. 

Bronze is an alloy of copper with tin, the tin being to the cop- 
per as about one to nine. This, you know, is much used in ma- 
king statues and smaller ornamental figures. Bell-metal is a kind 
of bronze, having more tin in it than ordinary bronze. 

Pewter is an alloy of tin with lead or antimony. What is call- 
ed Britannia- ware is a kind of pewter. When glass and earthen- 
ware were not as cheap as they are now, people very generally 
used to eat upon pewter platters and drink out of pewter mugs. 

Brass, I have told you, is an alloy of copper and zinc. There 
are various other alloys of these metals. You have heard of 
pinchbeck watches. These are made in imitation of gold watches. 
The pinchbeck differs from brass only in having more zinc in it. 
It looks like gold; why, then, is it not just as good? Because it 
will not keep on looking so. Gold, you know, does not tarnish. 
The oxygen of the air can not get any hold upon it at all ; but it 
can get hold of both the zinc and the copper that compose the 
pinchbeck. 

There is another alloy of copper and zinc, called tombac, which 



ALLOYS AND AMALGAMS. 113 

German silver. Teaspoons that melt in tea. Gold and silver coin. 

can be hammered into very thin leaves, making a spurious or 
false gold leaf. When this is finely powdered it is the so-called 
gold bronze. 

You have heard of late years a great deal about German sil- 
ver. There is no silver in this at all. It is an alloy of copper, 
zinc, and another metal called nickel. It is this latter metal that, 
by its whiteness, gives the alloy its likeness to silver. There is 
a mixture of silver, nickel, and copper, which is a very good sub- 
stitute for silver, and is much used for ornamental purposes. The 
proportions of thes* metals in it are, silver 30, nickel 25, and cop- 
per 55. 

There is an alloy which is sometimes made a source of amuse- 
ment. Teaspoons are manufactured from it, which will imme- 
diately melt if they are introduced into hot tea. This alloy is 
composed of bismuth, lead, and tin ; the proportions, bismuth 8, 
lead 5, and tin 3. 

The gold and silver in common use are not pure, but are alloys. 
This is true both of money and of the articles for use and orna- 
ment made of these metals. 

In the silver coin of the United States we have a tenth part 
copper. The object of the copper is to make the coin hard, so 
that it will not readily wear out. Silver used for other purposes 
ought to have just this proportion of copper. If it have more, 
the beautiful white lustre of the silver will be lessened. 

Gold is softer than silver. In order to harden it sufficiently, 
one tenth of the gold coin of this country is an alloy of copper and 
silver. The word carat is used in expressing the amount of 
pure gold in any alloy of it. This word means one twenty -fourth. 

H 



114 ALLOYS AND AMALGAMS. 

Amalgam on mirrors. Gold obtained by amalgamation. 

If, therefore, it is said of any specimen that it is 16 carats fine, it 
is meant that the pure gold is 16 parts out of the whole 24 ; in 
other words, that it is two thirds gold. So if it be said that a spec- 
imen is 18 carats fine, it is meant that 18 parts of the 24 is gold ; 
that is, that it is three fourths gold. 

Amalgams are mixtures of mercury with other metals. There 
is one of these with which you are very familiar. It is the sil- 
vering on the back of glass in mirrors. This is an amalgam of 
mercury and tin. It is put on in this way : Tin foil, that is, tin 
leaf, is first applied all over the glass ; then„mercury is poured 
upon this, and it unites with the tin, making an alloy or an amal- 
gam, as it is called. 

You can make an amalgam with copper by rubbing a copper 
cent over with mercury. 

In both alloys and amalgams there is manifested a kind of af- 
finity. If there were not, the metals would not unite any better 
than oil and water. There is sometimes a very pretty use made 
of the affinity which mercury has for gold ; it is used to separate 
the gold from substances with which it happens to be mingled. 
The material which has the gold in it is powdered, and then it is 
shaken up with mercury. The gold unites with the mercury, 
forming an amalgam. Even when the material contains but lit- 
tle gold it may be extracted in this way, the mercury taking it 
out of the company in which it is found. The dust of jewelers' 
shops is often managed in this way, to save the gold that is in it. 

You get, in this way, a solution of gold in mercury. It is a 
solution of a solid in a liquid, just as is the solution of alum or 
salt in water. Now how can we get the gold from this solution ? 



ALLOYS AND AMALGAMS. 115 

Common use of the word amalgamate. 

The solution is poured upon a closely-woven cloth, which allows 
most of the mercury to run through. The gold, with a little mer- 
cury, remains in the cloth. Then, by the application of heat, this 
mercury is driven off in vapor into the air, and the gold is left 
alone. 

This mode of obtaining gold is called the process of amalgama- 
tion. This word you will often hear applied to other subjects. 
When people agree together very well, or unite readily in their 
views and plans, they are said to amalgamate. It is as the gold 
and mercury readily unite. You see here an extended use made 
of a word which, when first used, was only applied to one thing. 
A very good example is this of one way in which language is 
built up and enlarged. 

Questions. — What is an alloy? What is the first difference mentioned between 
this and a compound ? What is another difference ? What is said of brass in re- 
gard to this ? What of type-metal ? What is said of examining printed letters with 
a magnifying glass ? What is bronze, and for what is it used ? What is bell-metal ? 
What is said of pewter and Britannia-ware ? What is pinchbeck ? Why is it not as 
good as gold ? What is said of tombac ? What is German silver ? Tell about the 
melting teaspoons. What is said of silver being alloyed with copper? What of 
gold ? Explain the meaning of carat. What are amalgams ? Explain the silver- 
ing on the back of mirrors. What is said of the amalgam with gold ? How is the 
gold obtained from the amalgam? What is said about the word amalgamation? 



116 ACIDS. 



What compose acids. Flowers of sulphur. Roll brimstone. 



CHAPTEE XYIII. 

ACIDS. 

I have told yon about the union of oxygen with metals form- 
ing oxyds. Now most of the acids in the world are formed by 
the union of oxygen with certain substances which are not metals, 
such as sulphur, phosphorus, etc. I will, therefore, now notice 
some of these substances, and the acids which oxygen forms with 
them. 

I have already told you much about two of the substances with 
which oxygen forms acids. One is carbon, with which oxygen 
forms the gas called carbonic acid ; the other is nitrogen, a gas 
with which oxygen forms that powerful liquid acid, nitric acid, 
commonly called aqua fortis. 

Sulphur is another substance with which oxygen unites to form 
an acid, called by the chemist sulphuric acid, the common name 
of it being oil of vitriol. We see sulphur ordinarily in two forms, 
roll brimstone and the flowers of sulphur. The flowers of sul- 
phur are obtained by heating the sulphur so as to make it rise in 
vapor, the vapor being condensed so as to form fine powder. 
The roll brimstone is obtained by melting the sulphur and letting 
it run into moulds. 

Sulphur is very abundant in nature. It is found as sulphur, 
and sometimes in beautiful yellow crystals, in the neighborhood 
of volcanoes ; but it is most abundant in combination with other 
substances. You have seen, in the chapters on the metals^ that 



ACIDS. 117 

Plaster of Paris. Sulphuric acid. Sulphurous acid gas. 

it is united with many of them, forming sulphurets. Then the 
mineral called gypsum, or plaster of Paris, of which there is a 
great deal in the world, has sulphur in it. And, besides, there is 
some sulphur in all vegetables and animals. It is the sulphur in 
egg that blackens a silver spoon, forming a sulphuret of silver 
over its surface. 

Sulphur and oxygen are mild substances, but, united together 
in certain proportions, they produce an acid of the most corrosive 
character. Neither sulphur nor oxygen, applied to your skin, 
hurts it ; but the acid composed of them, if applied to it, would 
stain, and sting, and eat it. 

If you burn phosphorus in oxygen or in air, which contains 
oxygen, the phosphorus unites with the oxygen and forms phos- 
phoric acid. This you saw in Chapter III. So, also, if charcoal 
burns in oxygen or air, it unites with the oxygen and forms car- 
bonic acid. But if you burn sulphur in oxygen or in air, it does 
not form sulphuric acid. The sulphur does not get its full sup- 
ply of oxygen as the phosphorus and carbon do. It must have 
a full supply to form sulphuric acid, but it is only partly supplied. 
"With this partial supply it forms a gas, which we call sulphurous 
acid gas. This is the gas that you smell when you burn a sul- 
phur match. 

In the phosphoric acid the phosphorus has got all the oxygen 
that it can be made to unite with. So, also, in the carbonic acid, 
the carbon has all the oxygen that it can have. But in the sul- 
phurous acid gas the sulphur has united with only two thirds of 
the oxygen that it can be made to unite with, and that it must 
unite with to form sulphuric acid. 



118 iTCIDS. 

How sulphuric acid is made. Its affinity for water. 

Now sulphuric acid is made by taking away oxygen from some 
substance that has a good deal of it, and giving it to this sul- 
phurous acid gas. I will tell you how this is done. The sul- 
phurous acid gas is made by burning sulphur, the oxygen of the 
air uniting with the sulphur to form it. Then, to obtain the other 
third of oxygen which is needed to turn it into sulphuric acid, 
this gas is taken into the presence of nitric acid. This liquid, as 
you learned in Chapter IV., has a great deal of oxygen in it. 
From this, then, the sulphurous acid gas gets the needed oxygen, 
and so becomes sulphuric acid. Just how this is done you are 
not old enough to understand yet, but I shall explain in full in 
another book for older scholars. 

Think now what would happen if sulphur, on burning in the 
air, should unite with enough oxygen to form sulphuric acid. 
Every time that any sulphur is burned the corrosive effects of the 
acid would be seen. If a sulphur match were burned, the acid 
which would drop from it would eat whatever it fell upon. 
Holes would be continually made in carpets and dresses. If it 
dropped upon your flesh it would eat that. You see, then, the 
wisdom and goodness of the Creator in making sulphur unite 
with oxygen differently from carbon and phosphorus. 

Sulphuric acid has a great liking or affinity for water. If it be 
left standing in an open phial it will increase every day by tak- 
ing moisture from the air. If it stand some months in a damp 
place it will gather so much water as to become two or three 
times as heavy as at first. 

If sulphuric acid and water be mixed together, there is pro- 
duced at once a considerable degree of heat. This may be shown 




ACIDS. 119 

Experiments with sulphuric acid. Phosphorus. Its inflammability. 

by some very interesting experiments. I will mention 
two. One is represented in Fig. 39. In the vessel a is 
sulphuric acid and water just poured in. In the test tube 
b is some ether, which boils with much less heat than 
water does. Stirring this test tube around in the acid 
and water, there is enough heat produced in a few moments to 
make the ether boil. Another experiment is this. Put some 
tow or cotton around a wine-glass, having some little bits of phos- " 
phorus placed among it so as to touch the outside of the glass. 
Pour some water in the glass, and then some sulphuric acid. 
The heat produced will set fire to the phosphorus, and, of course, 
by that to the tow. 

I will now tell you about phosphorus, which forms phosphoric 
acid by uniting with oxygen. This substance exists extensively 
in nature, but never by itself like sulphur. It is always united 
with other substances. It is commonly obtained from bones. 
There is between one and two pounds of this inflammable sub- 
stance in the bones of a full-grown person. 

Phosphorus is generally in the form of sticks. It is white, and 
has a waxy look. It is so fond of oxygen that it is "kept in water. 
Exposed to the air, it smokes. This arises from its uniting with 
the oxygen of the air. This smoking is really a slow burning ; 
and if it be in a dark place, light is given out. Phosphorus takes 
fire with so little heat that it is necessary to be very cautious in 
experimenting with it. We should always cut it under water, 
and on taking a piece out we should hold it with a pair of pliers 
or on the point of a knife. 

The smoke that arises from phosphorus when exposed to the 



120 ACIDS. 

A contrast. Solution of phosphorus in ether. Experiments with it. 

air is phosphorous acid. When phosphorus is actually burned 
phosphoric acid is formed, as you have before learned. Observe 
the difference between sulphur and phosphorus in this respect. 
Phosphorus, on mere exposure to the air, makes phosphorous 
acid, but sulphur must be actually burned to make sulphurous 
acid, as noticed on page 117. There is more oxygen in phos- 
phoric acid than in phosphorous acid, just as there is more in 
sulphuric than in sulphurous. 

I will mention some of the experiments that can be tried with 
phosphorus. 

To prepare for some of these, put a piece of phosphorus, of the 
size of a large pea, into a phial containing half an ounce (a table- 
spoonful) of ether. Cork the phial, and let it stand for some 
days, giving it a shake occasionally. Pour off the liquid into 
another phial. It is a solution of phosphorus, and is ready 
for use. 

Drop some of this solution upon the hands, and rub them 
briskly together. The ether will fly off in vapor, leaving the 
phosphorus on the hands. If you do this in the evening, and 
make the room dark, your hands will be covered with light. 
The reason is, that the phosphorus unites with the oxygen of the 
air, producing combustion. If you rub your hands, the light will 
increase, because the fire is made to burn more briskly. But 
what is the reason that the hands are not burned in doing this ? 
It is because there is so little of the phosphorus that there is very 
little heat produced. 

Moisten a lump of sugar with the solution of phosphorus, and 
drop it into hot water. The heat of the water sends both the 



ACIDS. 121 

A fire under water. Matches. Rat electuary. Vinegar. 

ether and the phosphorus up to the surface, and, when they get 
there, the oxygen of the air sets fire to the phosphorus, and this 
sets fire to the ether, and off they go in a flame together. 

Pour some of the solution upon some fine blotting-paper. The 
ether evaporates, and, after it is all gone, the phosphorus takes 
fire, burning up the paper. If the blotting-paper be laid upon 
something hot, the phosphorus and ether will burn together, just 
as when they rose from the hot water. 

Fig. 40. Phosphorus can be made to burn under water. 

If a stream of oxygen be directed by the tube a, 
Fig. 40, upon a bit of phosphorus under hot water, 
in the glass &, it will burn brilliantly, the oxygen 
uniting with the phosphorus in the burning. 

Phosphorus is so eager to unite with the oxygen 
in the air that a little friction produces heat enough 
to make it unite with it, and so quickly as to burn. 
For this reason, phosphorus is one of the ingredients of the sub- 
stance on the ends of matches. 

Phosphorus is a very poisonous substance, and is often used 
for destroying rats and mice. The rat electuary, as it is called, 
is dough with some phosphorus in it. One dram of phosphorus 
is mixed up with eight ounces of hot water and eight of flour. 

Acetic acid is that which we have in vinegar. It is spirits of 
wine or alcohol oxydized. Oxygen is added to the alcohol as it 
is added to sulphur to make sulphuric acid, or to phosphorus to 
make phosphoric acid. Vinegar is very commonly made from 
cider by letting the air come to it. In this case the oxygen of 
the air unites with the alcohol in the cider, and forms acetic acid. 




122 ACIDS. 

Acids in fruits. • Muriatic acid. An explosion produced by sunlight. 

The amount of this acid in vinegar is very small. There are only 
from two to five gallons in a hundred of the vinegar. The rest 
is mostly water. 

Tartaric acid is an acid that exists in many fruits, sometimes as 
acid, and sometimes united with potash, forming the substance 
which we call cream of tartar. This substance is in the juice of 
the grape, and gathers upon the inside of wine-casks from the 
wine. 

There are various other acids in different fruits, as the citric in 
lemons, oranges, currants, etc., the malic in apples and other fruits, , 
the oxalic in sorrel. 

There is a very remarkable acid, which I have not yet noticed, 
commonly called muriatic acid. It is composed of hydrogen and 
a very singular gas called chlorine. This gas, which has a pale 
greenish-yellow color, is one of the ingredients of common salt, 
and I shall tell you particularly about it in another chapter. 
There is one thing which is very curious about these two gases, 
hydrogen and chlorine, when they are mixed together. If they 
be mixed in the dark, and be kept there, they have no disposi- 
tion to unite ; but bring the mixture into the light, and the union 
takes place, forming the muriatic acid. If a beam of sunlight be 
thrown by reflection from a looking-glass upon the glass jar con- 
taining the mixture, the union is so rapid as to cause a violent 
explosion. To prevent any accident from the broken glass, a 
wire screen must be put over the jar before the light is made to 
shine upon it. 

The chemists call this acid hydrochloric acid. You can readily 
see the reason of the name ; it comes from the two gases which 



ACIDS. 123 

Aqua regia. Chloride of gold and common salt. Prussic acid. 

compose it. The hydrogen gives it the first part of its name, 
hydro, and the chlorine the latter part, chloric. 

What is commonly called muriatic acid is a solution of the 
hydrochloric acid, which is a gas, in water. There is a little 
more in weight of the water than of the gas. 

A mixture of this acid with nitric acid is called aqua regia, that 
is, royal water, because it is the only liquid that will dissolve 
gold, the king of metals. It is very curious that neither of these 
strong acids alone can affect the gold, but let them make the at- 
tack together, and this king submits at once. The^gold, in dis- 
solving, is changed into a compound. It is done in this way. 
The nitric acid makes the gas chlorine, that is in the muriatic acid 
with hydrogen, part company from the hydrogen. The chlorine 
thus set free, having a great liking for gold, unites with it, form- 
ing a chloride of this metal. "We do not get, therefore, a real 
solution of gold, but a solution of this chloride. Common salt is 
a chloride of a metal, and I shall tell you about this and other 
chlorides in another chapter. 

Another remarkable acid I will barely notice. It is commonly 
called prussic acid. It is a most deadly poison. A drop or two 
put upon the tongue of a dog will kill him instantly. This acid % 
is composed of carbon, nitrogen, and hydrogen. It exists in very 
minute quantities in bitter almonds, peach blossoms, the kernels 
of some of the stone fruits, etc., giving to them a peculiar odor 
and flavor. A flavor is often given to articles of food by the use 
of bitter almonds, peach-pits, etc. ; but the quantity of prussic 
acid thus used is so very minute that it does no harm. 

I told you, in the first part of this chapter, that most of the 



124 ACIDS. 

Hydrogen acids. 



acids have oxygen in them ; but prussic acid and hydrochloric 
acid have not. They have hydrogen instead, and so they are 
called hydrogen acids. There are not many of this class of acids 
compared with the oxygen acids. 

Questions. — How are most of the acids formed ? What two acids have you already 
learned considerable about? State some things in regard to them. What acid 
does sulphur form with oxygen ? Describe the two forms in which we have sulphur. 
What is said of the abundance of sulphur ? What of its combination with other 
substances ? Why does egg blacken the spoon with which you eat it ? What is said 
of the difference between sulphuric acid and the ingredients that compose it ? How 
do carbon and phosphorus differ from sulphur in uniting with oxygen ? How does 
sulphurous acid gas differ from phosphoric acid and carbonic acid ? Tell how sul- 
phuric acid is made. What would happen if sulphuric acid were formed whenever 
sulphur is burned ? What is said of the affinity of sulphuric acid for water ? What 
effect does this union produce ? Describe the experiment represented in Fig. 39. 
Give the other experiment. From what is phosphorus commonly obtained? De- 
scribe phosphorus. What care should be exercised in experimenting with it? Tell 
about the solution of phosphorus in ether. Tell what the effect is when some is put 
upon the face and hands, and explain it. Give the experiment with sugar. Give 
that with blotting-paper. Explain Fig. 40. What is acetic acid? Explain the 
chemistry of making vinegar. How much acetic acid is there in vinegar ? What is 
said of tartaric acid? Mention some of the acids found in plants. Of what is muri- 
atic acid composed ? Describe the influence of light upon the union of chlorine and 
'hydrogen. Explain the name hydrochloric given to muriatic acid. What is really 
the liquid commonly called muriatic acid? What is said of aqua regia? What of 
prussic acid ? What are hydrogen acids ? 



SALTS. 125 

Oxyds and acids united form salts. 



CHAPTER XIX. 

SALTS. 

I have told you about oxyds, which are formed by the union 
of oxygen with the metals. I have also told you about the acids, 
which are, most of them, formed by the union of oxygen with 
certain substances, as sulphur, phosphorus, carbon, nitrogen, etc. 
Now these acids unite with these oxyds to form what are called 
salts. 

The term salt is applied by the chemist to any substance com- 
posed of an acid and an oxyd. Thus nitric acid united with pot- 
ash forms the salt called by the chemist nitrate of potash, and by 
people generally saltpetre. So sulphuric acid united with potash 
forms the salt called sulphate of potash. It may seem odd to you 
to speak of chalk as a salt, but it is so called by the chemist be- 
cause it is composed of an acid, carbonic acid, and an oxyd, lime, 
together forming the carbonate of lime. 

Observe that the acids do not unite with the metals, but with 
the oxyds of the metals. Thus nitric acid does not unite with 
potassium, but with the oxyd of this metal, potash. It is so with 
all metals and all acids. In forming a salt a compound unites 
with a compound. The oxyd is a compound of oxygen and a 
metal, and the acid is a compound of oxygen and some substance, 
as sulphur. So it seems that there must be oxygen on both sides, 
or the acid will not unite. 

Observe the names of the salts. You can always tell by the 



126 SALTS. 



How the names of salts show their composition. 



name which the chemist gives to a salt of what it is composed. 
Thus, take nitrate of potash. The termination of the first word 
in the name is ate, and signifies that the substance is a salt, and 
the first part of the word shows what acid is in the salt. Then 
potash is the name of the oxyd, the other part of the salt. So, 
also, the acid in sulphate of potash is sulphuric acid, and that in 
carbonate of potash is carbonic acid. 

But there are some salts the names of which have the termina- 
tion of the first word in tie instead of ate. These salts are formed 
with acids whose names end in ous, while the salts which have 
ate in their names are formed with acids whose names end in ic. 
Thus sulphite of soda has sulphurous acid in it, while sulphate of 
soda has in it sulphuric acid. The salts whose names end in ate 
are much more common than those whose names end in tie. The 
former have more oxygen in them than the latter, for the acids 
that have their names end in ic have more oxygen than those 
whose names end in ous. 

Some of the metals have no special names for their oxyds, as 
potassium, sodium, etc., have. In such cases the name of the 
metal is used in giving the name of the salts. Thus we say car- 
bonate of iron. It would be more correct to say carbonate of the 
oxyd of iron. This would be too long, and so we leave out a 
part of the name. If this oxyd had any short name, as the oxyd 
of potassium has, we should use it. 

An acid and an oxyd are very different from each other. 
This is especially true of the alkalies. They have qualities just 
opposite to those of the acids. The taste of potash, for instance, 
is the very opposite of sour ; and all its other qualities, as you 



SALTS. 127 

Composition of cream of tartar, and the names given to it by chemists. 

will learn in my next book on Chemistry, are the opposite of 
those of an acid. But when an acid and an alkali unite together 
in certain proportions, the acid destroys all the alkaline qualities 
of the alkali, and the alkali destroys all the acid properties of the 
acid. 

The white powder which you know by the common name of 
cream of tartar is a salt composed of tartaric acid and potash. 
But this is sour, as you know, if you have ever taken it as a 
medicine. How is this? Why is it that in this case the acid 
properties are not destroyed by the alkali ? It is because there is 
not enough of the alkali united with the acid to do it. The salt 
is not as sour as the tartaric acid itself, for a part of the acid qual- 
ity is destroyed by the potash. 

There is another salt, made of the same ingredients, in which 
there is enough potash to destroy all the acid properties of the 
acid. It is called tartrate of potash, while the cream of tartar is 
called the st^ertartrate of potash. Cream of tartar has this name 
because there is more tartaric acid in it than there is in the tar- 
trate of potash. It is for the same reason that a thing is called 
superfine when it is more than fine, or superexcellent when it is 
more than excellent. 

Cream of tartar is sometimes called, also, the bitartrate of pot- 
ash. This is because the Latin word his means twice, for this salt 
has exactly twice as much tartaric acid in it as the tartrate of pot- 
ash has. So there is a carbonate of soda and a bicarbonate of 
soda. There is just twice as much carbonic acid in the bicar- 
bonate as in the carbonate. 

A salt in which there is just enough of alkali to destroy the 



128 SALTS. 



Neutral salts. Uses of the word neutralize. Affinity between unlike thing3. 

acid properties of the acid is called a neutral salt. You see the 
reason of this name. A neutral person is one who takes neither 
side in a dispute or a contest. Well, a neutral salt is neither on 
the acid nor the alkaline side ; and so, too, the acid and the alkali 
are said to neutralize each other in forming the neutral salt. This 
word is much used in regard to the common affairs of life. When 
some effort or influence destroys some other effort or influence, it 
is said to neutralize it. 

You see that it is not things which are alike, but those which 
are unlike, that have a liking or affinity for each other. Thus an 
alkali has no affinity for another alkali; but bring an acid to 
either alkali, and a union is effected at once. 

Questions. — What is a salt? Give some examples of salts, and state their com- 
position. Give some in addition to those mentioned here. What is particularly to 
be observed about the composition of salts ? What is said of their names ? Give 
the difference between the salts whose names end in ate and those ending in ite. 
Which kind have the most oxygen in them ? Which are the most common ? What 
is said of the name of carbonate of iron and of various other salts ? What is said of 
the opposite qualities of acids and oxyds ? What is said of their union ? Why is the 
salt called cream of tartar so sour ? Why is this salt sometimes called supertartrate 
of potash ? Why Sometimes called bitartrate ? What is a neutral salt ? What is a 
neutral person ? What is the meaning of the word neutralize ? What is said of 
chemical affinity ? 



CARBONATES. 129 



Chalk and marble. A comparison. Limestone. 



CHAPTEE XX. 

CARBONATES. 

The salts called carbonates are composed of carbonic acid gas 
united with oxyds of metals. There are very many of them. 
You have already learned some things about a few of them. I 
shall, in this chapter, tell you more about these, and notice some 
others that it will be interesting and useful for you to know 
about. 

The oxyd of calcium, commonly called lime, united with car- 
bonic acid, forms carbonate of lime. This salt appears under 
various forms. One, with which you are very familiar, is chalk. 
Another form of it is marble. One would hardly suppose that 
so hard a substance could be composed of exactly the same things 
as the crumbling chalk ; but we have many examples of a similar 
character. Sugar, in some forms, is very soft and crumbling; 
but rock-candy, as it is called, is exceedingly hard, and yet it is 
nothing but sugar. But we have another example, noticed in the 
chapter on carbon, which is much more striking. The diamond, 
which is the hardest and most brilliant of all known substances, 
is one form of carbon, while the dark and crumbling charcoal is 
another. 

This salt appears in many other forms, some of them crystals 
of great beauty. There is an abundance of it in the earth ; many 
hills and mountains are made of it. When it is in such large 
masses it has the common name of limestone. 

I 



130 



CARBONATES. 



Stalactites and stalagmites. 



Hall of Statuary in Weyer's Cave. 



Carbonate of lime does not readily dissolve in water. But wa- 
ter will dissolve some, especially if there be carbonic acid gas in 
the water. The water that comes from some springs has, for this 
reason, considerable of this salt in it, and some of it stops upon 
stones and sticks above the spring, crusting them over. In some 
caves in limestone regions we have beautiful displays of the forma- 
tion of limestone from water in which this salt is dissolved. As 
the water drips from any spot in the roof of the cave, some of the 
carbonate of lime stays upon the roof. Then, as more and more 
adheres, there forms a projection pointing downward, very much 
Fig. 41. like an icicle as water drips in 

cold weather from the eaves 
of a house. At the same time, 
there is formed underneath, on 
the floor of the cave, a little hil- 
lock of the limestone from the 
water that drops there. That 
which forms above is called a 
stalactite, and that below a sta- 
lagmite. 

Sometimes, when there are 
many of these stalactites and 
stalagmites, and they have been 
forming for a long time so as to 
reach a great size, they make a 
splendid appearance. In Fig. 
41 you have a picture of the 
Hall of Statuary, as it is called, in Weyer's Cave in Virginia. 




CARBONATES. 131 



Quick-lime. Carbonate of potash. Leach-tubs. 

Here the stalactites and stalagmites present every variety of form 
and arrangement, and, lighted up with torches, the place looks like 
a scene of enchantment. 

I have told you something about quick-lime on page 97. This 
is, as you learned there, the oxyd of calcium. It is commonly 
obtained from carbonate of lime. The limestone or the chalk is 
subjected to great heat in the flame of a furnace. This makes 
the carbonic acid quit the lime and fly off into the air. Lime, 
that is, the oxyd of calcium, is left behind. 

Carbonate of potash is a very different substance from carbonate 
of lime. It likes water very much, and dissolves in it readily. 
It exists in plants, and therefore is obtained from ashes. Not 
many years ago it was common for every family in the country 
to have what was called a leach-tub. In this were put the ashes. 
These being kept wet, there was always a running out, from a 
hole below, of a liquid called ley. This contained the carbonate 
of potash and caustic potash together in solution. There is caus- 
tic potash as well as the carbonate, because there is lime in ashes. 
The explanation is this : Lime, having a greater affinity for car- 
bonic acid than potash has, takes away this gas from some of the 
carbonate, thus changing it into potash. The quantity of the 
caustic potash in the ley is increased by putting some lime into 
the bottom of the leach-tub. The effect of this is to change much 
more of the carbonate of potash into caustic potash than would 
be changed by the little lime that is in the ashes. Leach-tubs are 
now very much out of use in families, as potash is made from 
ashes mostly in large establishments. 

This mixture of carbonate of potash and caustic potash is call- 



132 



CARBONATES. 



A contrast. 



An easy experiment. 



Fig. 42. 



ed simply potash by people generally, but this is not strictly cor- 
rect, for this name belongs properly only to caustic potash, that 
is, the oxyd of potassium. 

I have told you that if carbonate of lime be heated strongly, 
the carbonic acid is driven off. Carbonate of potash is very dif- 
ferent in this respect. The hottest fire can not drive off the car- 
bonic acid from it. If heat could do it we should not have any 
carbonate of potash in ashes, but caustic potash, the carbonic acid 
having been carried off by the burning into the air. 

Here is a little experiment that you can try with carbonate of 
potash. Drop a teaspoonful of this salt into a tumbler half full 
of vinegar. There will be a brisk effervescence, 
a gas escaping from the liquid. Lower, now, a 
burning taper into the tumbler, as represented in 
Fig. 42. It will go out. Why? Because the 
gas which comes up and fills the tumbler is car- 
bonic acid. The acetic acid in the vinegar takes 
the potash away from the carbonic acid, because 
it has a greater affinity for it. A salt is formed 
in this experiment by the union of the acetic 
acid and the potash. You can tell what the 
name of it is by observing what I have told you about the names 
of salts on page 126. 

If you dissolve some potash in water, and then boil in the solu- 
tion some dirty greasy rags, the solution will become very dark 
and dirty, but the rags will be white and clean. There is chem- 
istry in this. The potash has an affinity for the grease, and in 
the water we have the two united together; but in getting to- 




CARBONATES, 133 



Operation of soap explained. Some poetry about soap. 

gether, the dirt has been taken out of the cloth, with the grease, 
by the potash. This explains the use of soap in washing. In 
making common soft soap the potash is united with grease or fat 
and water, but there is not so much grease as to prevent the pot- 
ash from uniting with more grease. The potash alone would be 
a very harsh material to wash with, but by mixing it with grease 
and water we make a very smooth article that we can use easily. 
In washing clothes the potash in it takes out all the oily matter 
which has come from the perspiration, and with it the dirt ; and 
if there be dirt alone without any oily matter, the soap readily 
mingles with it, so that the water can. take it out better than it 
can without the soap. 

Here is some poetry which some one has written about soap : 

"Some water and oil 

One day had a broil, 
As down in a glass they were dropping, 

And would not unite, 

But continued to fight, 
Without any prospect of stopping. 

Some pearlash o'erheard — 

As quick as a word, 
He jumped in the midst of the clashing ; 

When all three agreed, 

And united with speed, 
And soap was created for washing." 

I must find a little fault with this poetry, pretty and amusing 
as it is. The water and oil do not have any " broil" when we try 
to mix: them together. They simply will not have any thing to 
do with each other. As soon as you stop skaking them in a ves- 



134 CARBONATES. 



Want of affinity between oil and water. Pearlash. Sal seratus. 

sel they very quietly take their places, the water being the heavi- 
est, and therefore taking the lowest place. You can pour oil in 
upon water, and the water, so far from quarreling with it, will let 
it be on top of it. The truth is merely that they have no liking 
or affinity for each other, and will not mingle in each other's com- 
pany, as water and alcohol will. But put some potash or pearl- 
ash in with them, and it will introduce them to each other, and 
all three will " agree" so well as to make together soap. 

You see that in this poetry the word pearlash is used. The 
potash that is obtained from ley is quite impure; that is, it is 
mixed with some other things. This is often called crude pot- 
ash ; but when it is purified it is called pearlash. 

There is a great deal more of chemistry in soap-making than I 
have told you, and I shall go farther into the subject in the book 
which I am preparing for older scholars. 

There is a bicarbonate of potash, a salt which has twice as 
much carbonic acid in it as the carbonate has ; its common name 
is sal ceratus. This is sometimes used for raising bread and cake. 
How does it produce this effect ? The acid that is used with it 
takes the potash from the carbonic acid, and this gas, set free 
every where in the dough, makes little spaces or cells, swelling 
up the dough. Sour milk is often used as furnishing an acid 
which will do this. 

There are two carbonates of soda, the carbonate and the bicar- 
bonate. That which has the most carbonic acid in it, the bicar- 
bonate, is used in making the soda powders which you see put 
up in boxes. The powder in the blue papers is this salt, and the 
powder in the white papers is tartaric acid. If you dissolve one 



CARBONATES. 135 



Carbonate of magnesia. White lead. Lead poisoning. 

kind of powder in some water in one tumbler, and the other kind 
in another tumbler, and pour the two together, an effervescence 
occurs. This is because the tartaric acid has a greater affinity 
for soda than carbonic acid has. It seizes the soda, therefore, and 
the carbonic acid gas set free, rising through the water, makes a 
great stir in it. 

There is a carbonate of magnesia. This is the common mag- 
nesia used in medicine. If this be heated very thoroughly the 
carbonic acid is driven off, just as it can be driven off from car- 
bonate of lime or chalk. This changes the carbonate into an 
oxyd of the metal magnesium. This oxyd is the so-called cal- 
cined magnesia, of which very probably you have taken some as 
medicine. 

The carbonate of lead is the white lead so called, which is used 
so much in painting. This is a very poisonous salt. It is on 
this account that persons have sometimes been made sick by 
sleeping in rooms that have just been painted. Some of the car- 
bonate of lead in the paint escapes into the air, and is breathed 
into the lungs. 

This salt is often formed in the lead pipes used for conveying 
water. And as it dissolves readily, it is carried into the system 
of those who drink the water, and gradually produces painful 
disease, which sometimes ends in death. What appears at first 
thought singular is, that the more pure is the water, generally the 
more apt is this salt to form. This is, however, easily explained. 
There are always oxygen and carbonic acid in water. These will 
act upon the lead, unless they are in some way prevented from 
doing it, in this way : the oxygen will make an oxyd of lead, 



136 CARBONATES. 



Sal volatile. 



and then the carbonic acid will unite with this oxyd to form the 
carbonate. Now when the water is not pure it commonly has 
some substances in it which act on the lead in such a way as to 
form a thin coat which is not soluble in the water. This pre- 
vents the oxygen and carbonic acid in the water from acting 
upon the lead. Fortunately, the substances dissolved in water 
are usually such as to make the fixed coating, and therefore most 
waters can be safely carried through lead pipes. 

I have alluded to the carbonate of ammonia on page 97. This 
is the common sal volatile, so called because it so readily flies off 
into the air, as you realize when you put a smelling-bottle to your 
nose. It is the fine particles of this salt that fly up into your 
nose and tingle it with its pungency. Ammonia is called harts- 
horn, because at first it was obtained by distilling the horns of 
deers and harts. It is now commonly obtained from bones. 

Questions. — Of what are carbonates composed? What is carbonate of lime? 
What is said of two of its forms, chalk and marble ? What is said of the abundance 
of this salt and of the variety of its forms ? What of its solubility ? What are sta- 
lagmites and stalactites ? How are they formed ? Tell about Weyer's Cave. How 
is quick-lime obtained ? How does carbonate of potash differ from carbonate of lime ? 
From what is it commonly obtained? What is said of the leach-tub ? What is said 
of the name potash as commonly used ? How does carbonate of potash differ from 
carbonate of lime as to the effect of heat upon it ? Explain the experiment repre- 
sented in Fig. 42. Explain the operation of potash upon dirt and grease. What is 
said of common soap ? Eepeat the poetry in regard to the making of soap. How is 
this not exactly true ? What is peaiiash ? How does the bicarbonate of potash dif- 
fer from the carbonate ? What is it commonly called ? How is it used in raising 
bread ? What is said of the two carbonates of soda ? What of carbonate of mag- 
nesia ? What is calcined magnesia ? What is white lead, and for what is it used ? 
What is said of lead poisoning? What is said of sal volatile? Why is ammonia 
commonly called hartshorn ? 



SULPHATES, NITRATES, AND ACETATES. 137 

Plaster of Paris. How compounds differ from their ingredients. Alabaster. 



CHAPTER XXI. 

SULPHATES, NITRATES, AND ACETATES. 

The most abundant of the sulphates is the sulphate of lime. 
This is sometimes called gypsum, and sometimes plaster of Paris. 
It received this latter name because there are immense quantities 
of it near Paris, and it was first used in that city as a plaster. 

Sulphate of lime is a very mild substance, and yet it is made 
of two very active substances. Lime is considerably caustic, and 
sulphuric acid is one of the most caustic substances in the world. 
Mix lime, as the gardener sometimes does, with weeds, and it will 
rot them quickly by its caustic power ; and if you drop sulphuric 
acid upon your skin it will eat it. But let the sulphuric acid and 
the lime unite together, and you have a substance that you can 
handle, and, when powdered and wet, you can mould it with your 
fingers. Here we have one of the most striking illustrations of 
the fact so frequently seen, that a substance may be wholly unlike 
the ingredients that compose it ; and lime and sulphuric acid are 
both also illustrations of the same fact. Oxygen, the life-support- 
ing gas, united with a metal, gives us the lime ; and united with 
sulphur, gives us the biting acid. 

Some of the forms in which gypsum is found in nature are 
very beautiful. The alabaster, which is cut into vases and other 
ornaments, is one of them. Sometimes this salt is arranged in 
delicate white fibres, and then it is called satin spar. It is well 
named, for it is as elegant as satin. Sometimes it is in very thin 



138 SULPHATES, NITRATES, AND ACETATES. 

Plaster casts. Copying coins in plaster. Hard-finish. 

leaves, laid closely together, and at the same time it is as clear as 
water. It is then said to he foliated, a word which comes from 
the Latin for leaf. The common word foliage comes from the 
same source. 

Gypsum is used in powder for a variety of purposes. In using 
it, the fact that one fifth of the substance is water is of great serv- 
ice. I will tell you how this is. Suppose that you wish to make 
a plaster cast. You subject the powdered gypsum to considerable 
heat to drive off this water that is in it. Then you wet it up so 
as to make a paste of it. With this paste you mould your figure. 
Then you let it stand till it becomes dry and hard. Observe 
what happens. Does the plaster merely dry as a wet cloth does ? 
that is, does the water which has been mingled with it pass off 
into the air ? Some of it does ; but a large part of it becomes a 
part of the plaster. The gypsum really takes to itself, and makes 
a part of its solid self, exactly as much water as it lost when it 
was heated. It is precisely as the quick-lime takes water into 
itself, as stated on page 97. 

You can take very pretty copies of coins or medals with this 
plaster. You can buy a little of it from which the water has 
been expelled. Moisten some of it, and put it into a small round 
paper box. Large-sized pill-boxes will answer. Press now your 
coin upon the surface of the plaster. When the plaster is dry 
and hard, take your coin off, and you will see a good impression 
of it in the plaster. To prevent the coin from sticking to the 
plaster, oil it very slightly. 

The hard-finish which is put upon our walls is made of this 
plaster from which the water has been driven off. First the wall 



SULPHATES, NITRATES, AND ACETATES. 139 

Glauber's and Epsom salts. Vitriols. A pretty experiment. 

is plastered with common lime mortar. Then some of the pow- 
dered gypsum is stirred up in water, so as to make a thin paste, 
and this is nicely spread upon the wall and left to harden. 

Sulphuric acid united with soda forms a sulphate of soda, or 
Glauber's salts, as it is called. This salt is in crystals of some 
size. With magnesia, sulphuric acid forms sulphate of magnesia, 
which is called Epsom salts. This is in the form of small very 
white crystals. It is really a very pretty substance, but it has a 
bitter, disagreeable taste, as you may well know if you have ever 
taken any of it as a medicine. Both of these salts are called neu- 
tral salts, for the acid properties of the sulphuric acid are wholly 
neutralized in them. There is no trace of acid in their nauseous 
taste. 

There are three sulphates that are in common language called 
vitriols. They are the sulphate of zinc, the sulphate of iron, and 
the sulphate of copper. The sulphate of zinc is white, and is call- 
ed white vitriol. The sulphate of iron is green, and is called green 
vitriol, and sometimes copperas. The sulphate of copper, or blue 
vitriol, has a fine blue color. 

You can try a very pretty little experiment with the sulphate 
of copper. Dissolve as much of this salt as you can in a little 
water. Hold the blade of your knife in the solution for a few 
minutes. On taking it out you will find it covered with a red 
coat, which is metallic copper. Think now how this happens. 
Here is some chemical affinity to be explained. Observe that 
there is in the water copper united with sulphuric acid. Now 
none of that copper can get upon your knife unless it be separated 
from the acid. How is it separated? Why, the acid liking the 



140 SULPHATES, NITRATES, AND ACETATES. 

Interesting fact about a mine. Alum. Gunpowder. 

iron better than it does copper, that which is close by the knife 
quits the copper to take the iron. It unites with the iron and 
forms sulphate of iron. This salt, as it forms, is dissolved in the 
water, and the copper clings to the iron, giving it the red coat. 

This experiment explains the manner in which the metal cop- 
per is sometimes obtained in some mines from a solution of this 
salt. At one time, in Wicklow, Ireland, five hundred tons of iron 
bars were placed in pits that were full of this solution of sulphate 
of copper. In about a year the bars were all gone. What had 
become of them ? The sulphuric acid in the sulphate of copper 
had quit the copper and united with the iron to form sulphate of 
iron. The copper lay at the bottom of the pits, in a sort of red- 
dish mud. This was taken out, and the copper freed from what 
was mixed* with it, and, by melting, was ]5ut into proper shape 
for use. 

Alum is a sulphate, but it is not a sulphate of one oxyd, as the 
sulphates are that I have mentioned. It is a sulphate of two 
oxyds ; it has two strings to its bow, as we may say. It is sul- 
phuric acid united with potash and alumina. Potash I have said 
so much about that you are well acquainted with it. Alumina I 
have noticed on page 108. Alum is a double salt, as it is termed. 
There are many of such salts. The medicine called tartar emetic 
is a double salt. It is a tartrate of potash and antimony. 

Nitrate of potash, formed by the union of nitric acid and pot- 
ash, is commonly called either nitre or saltpetre. It is chiefly 
interesting as being one of the ingredients of gunpowder. This 
article is made of three things, nitre, charcoal, and sulphur. They 
are very carefully mixed. When fire is touched to this mixture 



SULPHATES, NITRATES, AND ACETATES. 141 



Explosion of gunpowder explained. Lunar caustic. . Sugar of lead. 

it readily burns, and in the burning a great quantity of gas is 
produced all at once. It is this gas, striving to get room for it- 
self, that drives the ball out of the gun or cannon, as is fully ex- 
plained in the chapter on Powder in the Third Part of the Child's 
Book of Nature. 

But how is this gas produced ? Let us look at this. The nitre 
is composed of nitric acid and potash. Now there is oxygen gas 
in both nitric acid and potash, and this oxygen quickly unites 
with the carbon or charcoal, forming a great amount of carbonic 
acid gas. In doing this it sets free the nitrogen gas which was 
with it in the nitric acid, this acid being composed, as you learned 
in Chapter III., of oxygen and nitrogen. Carbonic acid gas and 
nitrogen are then the chief gases that are set free in firing gun- 
powder, and produce the explosion. 

Think how great the change is in this case. From a small 
quantity of powder comes out, all at once, a very large bulk of 
gases. I say comes out, for the gases were in that powder locked 
up, and squeezed, as we may say, into small quarters. And see 
what it is that sets free these condensed gases. It is our lively 
friend oxygen, waked up by fire to assert its affinities. 

I will notice only one other nitrate, the nitrate of silver. This 
is a white caustic salt. It is used in making indelible ink. It is 
used also in the fixtures for coloring the hair dark. 

The acetate of lead is commonly called sugar of lead, because 
it has a sweet taste. It seems strange that it should have such a 
taste when one of its ingredients is so sharp an acid. You can 
have some idea of its sharpness when you call to mind that it 
makes but about the twentieth part of the sharpest vinegar. 



142 SULPHATES, NITRATES, AND ACETATES. 

Making a lead tree. A comparison. 

I will describe a beautiful experiment that you can try with 
this salt. Dissolve half an ounce of sugar of lead in six ounces 
(twelve tablespoonsful) of water, in a phial. Fasten in the cork 
a rod or stick of zinc, as you see in Fig. 43. You will soon see a 
change taking place. The zinc will begin to have little spangles 
upon it, and these will gradually branch out in all directions, 
Fig. 43. forming a sort of tree. This tree is made of the 
metal lead, and is called the lead tree.* The ex- 
planation is this. The acetic acid has a stronger 
affinity for zinc than it has for lead. It therefore 
leaves the lead and unites with the zinc to form 
acetate of zinc. The lead, which is separated from 
the acid, forms the tree, while the acetate of zinc 
dissolves in the water, taking the place there of the 
acetate of lead. It takes a day or two for the tree 
to be completed. If, on making the solution in the phial, it is 
not perfectly clear, you can make it so by adding a little good 
vinegar. 

The change of the acid in this experiment from the lead over 
to the zinc is like the change of sulphuric acid from the copper 
to the iron in the experiment with sulphate of copper given on 
page 139. In both cases the acid quits one metal to unite with 
another which it likes better. 

* This tree can be made to have different shapes by a little contrivance. Fasten 
a small lump of zinc to the under side of the cork by a string through the cork. 
Then fasten to the zinc some fine brass or copper wire, which you can make branch 
out in various directions. The crystals of lead will collect on these branches, and 
this will give a more perfect tree shape than the slip of zinc will. 




SULPHATES, NITRATES, AND ACETATES. 143 

Verdigris. Cooking in copper vessels. 

I will notice but one other acetate, that of copper, commonly 
called verdigris. This is a green-colored salt, and is very poi- 
sonous. It is used in painting. Whenever acetic acid comes in 
contact with copper, this salt is formed. You can see, therefore, 
how dangerous it would be to have any cooking operation in 
which vinegar is used done in a copper vessel. 

Questions. — What are the chemical name and composition of gypsum ? Why is it 
called plaster of Paris ? What is said of the difference between gypsum and its in- 
gredients ? What of the difference between lime and sulphuric acid and their in- 
gredients ? What is alabaster, and for what is it used ? What is satin spar ? What 
is meant by foliated gypsum ? Explain how gypsum is used in making casts. How 
can you copy coins with powdered gypsum ? What is said of hard finish ? What 
are the chemical name and composition of Glauber's salt ? What are Epsom salts ? 
Why are these two salts called neutral salts? Give the chemical name and com- 
position of the three vitriols. State the knife-blade experiment. State and explain 
the facts in regard to the copper-mine in Ireland. What are the chemical name 
and composition of alum ? What are double salts ? Give the chemical name and 
composition of tartar emetic. What is the composition of saltpetre ? Of what is 
gunpowder composed? How does it exert such force when fired? What are the 
gases set free in discharging it, and how are they produced ? What is said of the 
change produced in the powder ? What is said of the nitrate of silver ? What of 
the acetate of lead ? Describe and explain the formation of the lead tree. How is 
the change here like that in the copper-mine related on page 140 ? What is said of 
the acetate of copper ? 



144 SHELLS, CORALS, AND BONES. . 

Composition of shells. Oysters swallowing their shells. 



CHAPTER XXII. 

SHELLS, CORALS, AND BONES. 

The shells that you pick up on the sea-shore are made of car- 
bonate of lime. All oyster-shells are made of this substance. 
The lime which is used for making mortar and other purposes is 
often obtained from oyster-shells, just as we obtain it from lime- 
stone. It is obtained by burning them ; that is, by heating them 
very strongly. The heat, as you have before learned, drives off 
the carbonic acid gas, and leaves the lime alone. 

From whence comes all this carbonate of lime of which the 
shells are made ? It is in the water, dissolved in it as the salt is. 
But how does it get into the water ? It comes from the earth and 
the rocks of limestone. It is washed along with the water as it 
runs in brooks and rivers, and at length comes to the sea. Here 
there is more of it in the water than any where else. 

But how, think you, is this carbonate of lime made into shells? 
Does it gather from the water on the outside of the animals that 
live in them? Does the oyster, for example, just lie still, and let 
the shell grow on him by having the carbonate of lime settle upon 
him by little and little from the water, as it crusts upon a stone 
or a stick in a spring? No, this is not the way. All that big 
rough shell has been swallowed by the oyster, and has been in 
his blood. Only a little at a time was swallowed, dissolved in 
the sea-water ; but that little was used in building his shell-house 
to cover him. 



SHELLS, CORALS, AND BONES. 145 

How an oyster's shell is made. How coral animals grow. 

Look at an oyster's shell carefully. There are different layers. 
The outside layer is smaller than the next one, and this is smaller 
than the next, and so on ; and the one next to the oyster is the 
largest. The outside layer was made when the oyster was very 
small — a baby oyster, as we may say. Then, as he grew a little 
larger, another layer was formed from the carbonate of lime as it 
oozed out from his skin, and so on to the last and largest. 

All shells are not made exactly after the plan of the oyster- 
shell ; but it is as true of them all as it is of the oyster-shell, that 
every particle of them has been swallowed in the water drank by 
the animals that lived in them. 

There is one class of animals that live in the sea which make a 
singular use of the carbonate of lime that they continually swal- 
low. I mean the coral animals, as they are called. These little 
animals always stay exactly where they are born. They are 
fixed to a strong foundation. That foundation is their skeleton, 
formed from the carbonate of lime which they have swallowed. 
This skeleton extends up into the animal's body. The animal is 
all the time growing upward in the water, and adds continually 
to the top of its skeleton. In the mean time the lower part of its 
body is always dying. It dies below while it grows above. 

You see what the effect of all this is. The animal is building a 
column of carbonate of lime, he being all the time at the top of it, 
sitting on it like a well-fitted cap. 

But these animals always live in companies and build together. 
If a great many of them, then, build together their columns along- 
side of each other, there will be a great deal of building done, 
though each does but little. 

K 



146 SHELLS, CORALS, AND BONES. 

Coral animals reef-builders. All Florida made by them. 

You will be surprised when I tell you that whole islands have 
been built in this way. Long ranges of coast, sometimes for 
hundreds of miles, have been lined with reefs built up by these 
little animals. Some of the tiny builders that do such work are 
no larger than the head of a pin. 

These little reef-builders have done a vast deal of work in one 
part of our country — in Florida ; and they are engaged in the same 
work now. Once there was no Florida. The peninsula we call 
by this name was not there. The sea covered what is now dry 
land. This was centuries upon centuries ago. Florida, since 
that, has been built up, and the work has been done by the little 
coral animals. All the foundation of Florida has been gathered 
from the water by them. Yes, it had to be actually swallowed 
by animals before it could be made into Florida. 

I will show you a little how this building was done. All along 
the coast of Florida, a little way out from the main land, there are 
islands called keys. These have been built up by the coral an- 
imals. They began their work down deep at the bottom of the 
sea, and worked along upward till they reached the surface. Then 
their work was done, for they can not work out of water ; and 
their work being done, they died. 

But something more needs to be done to make these coral reefs 
fit to live upon, for they are merely plains, as we may call them, 
of carbonate of lime, which just come to the surface of the water, 
and when it is high water they are entirely covered. After a 
while they do become real islands, and things grow upon them, 
and people live there. I will tell you how this is done. The 
waves, dashing over the reefs, break them up somewhat, and the 



SHELLS, CORALS, ASTD BONES. 147 

The way in which the coral animals made Florida. 

pieces are washed up toward the middle of the reef. At the same 
time, the dirty stuff of various kinds washed about in the sea col- 
lects there also, and the sea-weed is thrown up upon the heaps in 
considerable quantities by the waves. All this gradually forms a 
soil upon the reef, and makes it a real island. Seeds are dropped 
there by birds, or are carried there in the water, and are washed 
up on to the land. Grass, flowers, shrubs, and trees soon grow 
there, and then man comes and plants such things as he wishes to 
have grow, and builds his habitation. 

These islands along the coast of Florida will, after a while, join 
to the main land ; that is, become a part of Florida itself. How 
is this ? The space between the main land and the islands is con- 
tinually filling up with mud, which washes in there, and after a 
long time there will be so much of it as to make dry land. All 
Florida has been made in this way. Island after island has been 
built up by the coral animals, covered with soil, and then joined 
to the main land in the way that I have pointed out. 

But you will ask why the coral-builders do their work away 
from the main land, instead of building up upon the edge of the 
shore. This is because the work is begun by coral animals that 
are fond of deep water, and can not live in shallow water. They 
work away, swallowing stone and laying it down, till they come 
up somewhere near the surface of the water. Their work is now 
done, and they die. Then another set of coral-builders, that are 
fitted to live in shallow water, go to building on the foundations 
laid by their deep-water friends. 

Different kinds of coral animals have different fashions in build- 
ing. There are beautiful specimens of their various work to be 



148 SHELLS, CORALS, AND BONES. 

Of what egg-shells are made. Of what bones are made. 

seen in mineral cabinets. These specimens are, as I have before 
said, really the skeletons of the animals. 

Egg-shells are made of carbonate of lime ; but hens sometimes 
lay eggs with no shells on them. Why is this ? It is because 
the hens have not swallowed enough carbonate of lime. They 
swallow it mingled with their food, the dust of it being scattered 
about from broken oyster-shells, chalk, etc. As the canary bird 
pecks away at the cuttle-fish bone that hangs in its cage, some of 
the dust of it becomes mingled with its food, and, being swallow- 
ed, is used in making the shells of the eggs that she lays. 

The bones of animals are made chiefly of a salt of lime, but 
not the carbonate ; it is the phosphate, a compound of phosphoric 
acid and lime. The three ingredients in this salt, then, are phos- 
phorus, oxygen, and calcium. Phosphorus is made from bones ; 
that is, it is obtained from bones by separating it from the oxygen 
and the calcium that are united with it. There is a great deal of 
phosphorus in bones — how much I have told you on page 119. 

The phosphate of lime that is in our bones is swallowed in our 
food, and so gets into the blood and goes to the bones, where it is 
wanted to make them grow. There is some of this salt in both 
our kinds of food, the animal and the vegetable. There is some 
of it in the milk upon which the infant lives. 

You see, then, that it is with the phosphate of lime in our 
bones as it is with the carbonate of lime in the shells of oysters 
and other shell-fish, in the stony skeletons of coral animals, and 
in the egg-shells of birds. The building material is swallowed, 
and, going into the blood, is carried in it to where it is wanted for 
building. 



SHELLS, CORALS, AND BONES. 149 

Materials for bones and shells come from the rocks. 

Think, now, from whence came all the carbonate and phosphate 
of lime that are in the bones and shells of animals. They came 
from the rocks. Yes, the phosphate of lime in your bones was 
once in the rocks, strange as it may seem to you. But how did 
it get from the rocks into your bones? A great deal of breaking 
up, grinding, etc., was necessary for this. There is crumbling 
from the rocks all the time, from the influence of frost, and water, 
and wind. Then what crumbles mixes with the earth, where it 
is jostled and rubbed about, and some of it thus becomes divided 
up very finely. Particles of it, therefore, continually get into 
plants in the sap which the roots suck up. If you eat vegetables, 
then, or the meat of an animal that has eaten vegetables, you in- 
troduce into your stomach, and so into your blood, some of the 
phosphate of lime that has come from the rocks. 

Questions. — Of what are shells made ? How is lime obtained from shells ? From 
whence does the carbonate of lime in the water come? How is it made into shells ? 
Describe the manner in which the shell of the oyster is formed. What is said of the 
formation of shells generally ? Describe the manner of the growth of the coral an- 
imal. What is the result of this process? What is the result if many of them are 
alongside of each other ? What is said of the extent of their building ? What is 
said about Florida ? Tell about the formation of the keys on the coast of Florida. 
When the coral animals have finished their work, how are their reefs made into 
islands ? Now tell how Florida itself was made. Why is it that this building of 
the coral animals is done away from the main land ? What is said of the different 
fashions of coral builders ? What is said of egg-shells ? What of the cuttle-fish 
bone in the cage of the canary bird ? Give the name and composition of the salt 
that is in bones. How much phosphorus is there in our bones ? What is said of the 
presence of phosphate of lime in our food ? Give the comparison between the mak- 
ing of bones and of shells. What is said of bones and shells being made out of rocks ? 



150 GLASS AND EARTHENWARE. 

Glass and earthenware salts. Flint and quartz an acid. 



CHAPTER XXIII. 

GLASS AND EARTHENWARE. 

You will think it strange when I tell you that, in treating the 
subjects named at the head of this chapter, I shall introduce you 
to a certain class of salts. Yet, surprising to you as it is, in glass 
and earthenware we have salts made with an acid, like the other 
salts of which I have told you. 

The acid which is in these salts is of a very peculiar character. 
Most acids, you know, are decidedly sour to the taste, and are 
liquid, as sulphuric acid, nitric acid, acetic acid, etc. There is, in- 
deed, one acid that I have told you much about, carbonic acid, 
which is a gas, and has rather a pleasant, lively, but scarcely acid 
taste, as you perceive in drinking soda-water. But the acid which 
we have in glass and earthenware is much more singular than 
this. It has no taste, and is solid, very solid. It is the substance 
which you see in flint, and in quartz or rock crystal, as it is called. 
The shining, clear grains which you see in sand are composed of 
this acid. It is called silicic acid, or silica. The latter is the 
name most often given to it. Very hard substances are these 
grains in the sand, and, if you put them into your mouth, so far 
from being sour, they are entirely tasteless. 

Why, then, is this silica considered an acid ? For several rea- 
sons, which I will now give you. 

One reason is, that, like most of the acids which I have men- 
tioned, it is composed of oxygen united with another substance. 



GLASS AND EARTHENWARE. 151 

Proofs that silica is an acid. How silica gets into plants. 

Thus, as sulphuric acid is composed of oxygen and sulphur, and 
carbonic acid of oxygen and carbon, so silicic acid, or silica, is 
composed of oxygen and a substance called silicon. 

Another reason is, that silica acts like the acids in regard to 
other substances. Thus, as sulphuric acid unites with lime, form- 
ing sulphate of lime, and carbonic acid unites with it to form car- 
bonate of lime, so silica, or silicic acid, unites with lime to form a 
substance which we call silicate of lime. 

But perhaps you will ask, why not consider this silica an oxyd 
instead of an acid — an oxyd of silicon — as it is composed of sili- 
con and oxygen ? First, because nearly all oxyds are formed 
with metals, and silicon does not appear at all like a metal. Then, 
again, if silica were an oxyd, it should unite with acids to form 
salts, as the oxyds do ; but this it can not in any way be made to 
do. On the other hand, it unites with oxyds, as is the case with 
other acids. 

Silica is a very important part of some plants. It is in the 
stalks of all grass, giving them such firmness that they can stand 
up. It is also in the stalks of all grain. It is to these and some 
other plants very much what bones are to animals. In some 
plants there is so much of silica that they are used for scouring. 

But how does this flint or silica get into plants? If you even 
make it very fine indeed, and put it into water, none of it will 
dissolve. It seems strange, then, that any of it should go with 
the sap up into any plant. To do this, it must be made very fine, 
much finer than we can make it by pounding and grinding ; and 
this is done in some way, we know not how, about the roots of 
plants. But this is not enough ; it must be changed so as to make 



152 GLASS AND EARTHENWARE. 

Glass in old mortar. Composition of common -window-glass. 

it dissolve in water, or it will not go up in the sap ; and this is done 
by means of the potash that is in the ground with the silica. But 
little is required, and that little is furnished dissolved in the sap. 
And then, as it goes up, it is lodged just where it is wanted in the 
stalk. None of it gets by mistake into the kernels of the grains. 
If it did so our flour would be gritty, and our teeth would be 
soon worn out. 

You know that in making mortar we put in sand with the lime. 
This gives firmness to the mortar. Lime and water would not 
answer alone. But the sand has another effect ; the longer the 
mortar or plastering remains, the harder does it become; and very 
old plastering, as we see in tearing down old houses, is very hard 
indeed. This is because the silicic acid in the sand gradually 
unites with the lime ; so that, in the course of years, there comes 
to be considerable silicate of lime, or glass, in the plastering. Old 
plastering is, then, a mixture of glass with the mortar. The glass 
is scattered through it, mingled with the lime and sand, making 
the whole very firm and hard. 

Glass is not one silicate alone commonly, but a compound con- 
taining two or more silicates. Thus common window-glass is a 
silicate of both lime and soda together. To make it there are 
melted together, with a very hot fire, fine nice sand, old glass, 
chalk, and soda. Chalk, you know, is carbonate of lime. The 
heat drives off the carbonic acid, and the lime, released from this 
acid, unites with the silicic acid of the sand, forming silicate of 
lime. At the same time the soda unites with this acid, making 
silicate of soda, and the two silicates, uniting in one, form a silicate 
of lime and soda. This, you see, is a double salt, as alum and tar- 



GLASS AND EARTHENWARE. 153 

Soluble glass. Discovery of glass. Composition of clay. 

tar emetic are, as noticed on page 140. The different kinds of 
glass are, you know, insoluble ; but there is a way of making glass 
that will dissolve, and it is used as a fire-proof varnish. 

The various colors of glass are made by various oxyds of met- 
als mingled with the melted glass — oxyds of iron, copper, manga- 
nese, etc. 

It is stated somewhere that the making of glass was discovered 
by accident. Some people going on a voyage were driven on 
shore at a very sandy place. There was a great deal of sea-weed, 
which had been thrown up upon the shore, and had dried in the 
sun. "With this they made a fire on the sand, and it was observed 
that there was mingled with the ashes some substance that was 
hard, and had a glassy appearance : it was really glass. You see 
the explanation of this. The ashes furnished the alkali and the 
sand the silica to make the silicate, that is, the glass. If this be 
all true, it is one of many examples which we have illustrating 
the fact that a vast deal can be often learned by thinking about 
the common things that we happen to see. A glassy appearance 
in the ashes of sea- weed most people would not spend a thought 
upon; but an observer, that is, one who thinks about what he 
sees, inquires what causes this appearance, and, in pursuing the 
inquiry, perhaps makes a valuable discovery. Be not, then, mere 
sight-seers as you go through the world, but observers ; and ob- 
serve little things as well as great. 

We have clay in all earthenware. It is quite pure in porcelain, 
and very impure in common flower-pots, and especially in bricks ; 
that is, it is mingled with other things, sand, etc. 

Clay is, like glass, a silicate. Perfectly pure clay is a silicate 



154 GLASS AND EARTHENWARE. 

Bricks. Flower-pots. Glazing. 

of alumina. But all clay, as we find it, contains more or less of 
other silicates, of lime, of potash, etc. 

The brownish-red color of bricks and common flower-pots is 
owing to the rust of iron which is in the clay. 

Bricks, you know, are quite porous, and so water will soak into 
them. This is, also the case with common flower-pots. This 
porousness will do us no harm in this case, but generally it is 
necessary to have earthenware so made that no fluid can. escape 
through its pores. It would not answer, for example, to keep 
preserves in jars of porous earthenware. The watery part would 
gradually escape through the pores, and the preserves would be- 
come dry. 

The difficulty is remedied in two ways. One is to glaze the 
surface of the earthenware; that is, a glass surface is made. 
This is done in various ways. One method you will be interested 
in, because you can understand the chemistry of it. The fumes 
of common salt are made to go up all about the articles of earth- 
enware when they are very hot. Now salt is composed of the 
gas chlorine and the metal sodium. I told you a little about 
chlorine on page 122, and I shall tell you more particularly about 
it in the next chapter. You learned something about sodium in 
Chapter XIV. In the glazing the chlorine leaves the sodium to 
unite with some of the iron in the earthenware. Then the so- 
dium, thus left by the chlorine, becomes soda by taking some ox- 
ygen ; and this soda unites with the silica in the earthenware to 
form a silicate of soda, thus making a soda glass, as we may call it. 
So you have a coating of this glass all over the articles. 

Another mode of making earthenware impervious to water 



GLASS AND EARTHENWARE. 155 

Earthenware which is partly glass. 

is to make the ware partly earthen and partly glass. The in- 
gredients are so selected that you may have the silicates of lime, 
potash, etc., of which glass is made, thoroughly united with the 
silicate of alumina or clay. This stops up all the pores, and does 
not merely shut those which are outside, as the glazing does. 

Questions. — To what class of substances in chemistry do glass and earthenware be- 
long ? What are the qualities of most acids ? How does carbonic acid differ from 
them ? What is silica ? In what substances do you see it ? How is it unlike other 
acids ? What is the first reason given for calling it an acid ? What is the second 
reason ? Why do we not call silica an oxyd ? What is said about its being pres- 
ent in plants ? How does it get into them ? What is said about its being deposited 
in the right place? Tell about silica in mortar. What are the salts made by silica 
called ? What is common window-glass ? Tell how it is made, and explain the 
chemistry of the process. What is said of soluble glass ? How are the various col- 
ors of glass produced ? Relate the anecdote about the discovery of the way to make 
glass. What truth does this illustrate ? What is in earthenware ? How is it in 
porcelain, in flower-pots, in bricks? What is the composition of pure clay? What 
else is there commonly with it? What is the cause of the brownish-red color of 
flower-pots and bricks ? What is said about their porousness ? What is glazing, 
and what is the use of it ? Describe and explain glazing with salt. Describe an- 
other way of making earthenware impervious to water. 



156 CHLORINE, BLEACHING, AND COMMON SALT. 

Composition of common salt. Properties of chlorine. 



CHAPTER XXIV. 

CHLORINE, BLEACHING, AND COMMON SALT. 

The salts which I have noticed in the previous chapters are 
made with acids : but there are some salts in which there is no 
acid. They are formed by the union of certain simple substances 
with a metal. Common salt is one of these salts. In this sub- 
stance we have, as stated in the previous chapter, the metal so- 
dium united with a very singular gas called chlorine, and so the 
chemists call it the chloride of sodium. 

You remember that all the compounds of the gas oxygen form- 
ed with metals are called oxyds, or oxides, as it is sometimes 
spelt ; so all the compounds of this gas chlorine are called chlo- 
rides. Salt is a chloride of sodium, as soda is an oxyd of it. 

Before I tell you particularly about salt I will speak of the gas 
chlorine. It is one of the gases that has color. Its color is a 
greenish-yellow. It has a powerful and very peculiar odor. It 
is very injurious if breathed in any quantity. Even when diluted 
with considerable air it is very suffocating. If you should breathe 
it without any air mixed with it you would die. Yet to breathe 
a very little of it, mixed with a great deal of air, does no harm, 
and it is supposed by some physicians that it is beneficial to those 
who have consumption. 

Chlorine is of great use in purifying foul air. You perhaps 
have seen chloride of lime, moistened, set round in dishes where 



CHLORINE, BLEACHING-, AND COMMON SALT. 157 

Chlorine a purifier of air. Bleaching with chlorine. 

there is sickness of such a kind as to cause bad odors. It is the 
chlorine that comes from this that purifies the air. The little 
chlorine that escapes into the air in this case, although you smell 
it pretty strongly, does no harm to your breathing, for it is very 
largely diluted with air. 

The odor of this gas is so peculiar that if you have ever smelled 
it once you always know it afterward. You smell it wherever 
there is bleaching of cloth going on. You smell it, therefore, 
in paper mills, for the rags out of which the paper is made are 
bleached by it. 

I will tell you about this bleaching. If you put a rag of calico 
into a jar of chlorine gas, no effect will be produced on its colors ; 
but moisten the rag before it is put in, and the colors will be 
taken out by the chlorine at once. Chlorine must have water 
present, or it will not bleach. 

Chlorine gas will dissolve in water, and the solution is very 
convenient to use in bleaching. A calico rag dipped in it is very 
soon made white. It will take out ink-spots also. It has no ef- 
fect upon printers 7 ink, however, nor can it bleach woolens. 

You see the great usefulness of chlorine in making paper. 
White paper can be made out of rags of all colors, because the 
colors can be removed by the chlorine. You see, too, its useful- 
ness in whitening cloth. The old method of doing this was very 
slow. It was to spread cloth out upon grass for the sun, and rain, 
and dew to whiten. This, called grass-bleaching, took weeks ; but, 
with the quick bleaching by chlorine, we can do the same thing in 
a few hours. Some care is required not to have the chlorine 
water too strong, and to get all the chlorine out of the cloth after 



158 



CHLORINE, BLEACHING, AND COMMON SALT. 



Modes of obtaining chlorine. 



Fig. 44. 



the bleaching is done. If this care is not exercised the cloth will 
lose some of its strength, some of the substance of the cloth being 
eaten out as well as the coloring matter. 

Exactly how chlorine bleaches you are not sufficiently ad- 
vanced in chemistry to understand, and that I shall explain in my 
next book. 

You can make chlorine in this way. Pour into a pint bottle 
two tablespoonsful of common sulphuric acid, and add a little 
more than the same quantity of chloride of lime, or bleaching 
powder. Add the powder gradually, covering the bottle with a 
slip of glass each time after dropping some in, as rep- 
resented in Pig. 44. Chlorine made in this way will 
answer for many of the experiments. 

The explanation is this : The sulphuric acid, hav- 
ing a stronger affinity for lime than chlorine has, 
takes the lime and unites with it. The chlorine, be- 
ing thus separated from the lime, rises up and fills 
the bottle. 

Another method is to put some black oxyd of manganese into 
a flask, and pour in enough muriatic acid to cover the oxyd, as 
seen in Fig. 45. Gentle heat must be applied, and the gas will 
Fig. 45. pass over into the bottle which is placed to receive 
it. You observe that the tube reaches to the bot- 
tom of the bottle. This is to have the chlorine gas 
push up the air which is in the bottle, which it 
readily does, taking its place in the bottle. It is 
two and a half times as heavy as air, and so has no disposition to 
escape upward. You can tell when the bottle is full by the color. 





CHLORINE, BLEACHING, AND COMMON SALT. 159 

Experiments with chlorine. Common salt and its ingredients contrasted. 

When it is full slip it out from under the tube, cork it, and place 
the tube in another bottle. 

The explanation of the formation of chlorine in this way is 
easy. The oxyd of manganese has a great deal of oxygen in it, 
while the muriatic acid is composed of hydrogen and chlorine, as 
you learned on page 122. The hydrogen of the acid unites with 
the oxygen of the oxyd of manganese, so that the chlorine of the 
acid is set at liberty. 
Fig. 46. Although chlorine gas is so destructive to life when 
breathed, it supports combustion. If a taper, Fig. 46, be 
introduced into a bottle of this gas, it burns with a dull 
red flame, and a thick cloud of smoke. The explana- 
tion is this : Chlorine has a strong affinity for hydrogen, 
but none for carbon. It therefore unites with the hy- 
drogen of the taper or candle, and the flame, heating the 
carbon that is with the hydrogen in the taper, sends it upward in 
a dense smoke. 
Fig. 47. So, also, if a slip of paper, moistened with oil of turpen- 
tine, be introduced into a bottle of chlorine, Fig. 47, the 
hydrogen of the turpentine will burn, while its carbon 
will pass off unburnt in smoke. 

See how very widely both of the ingredients of salt 
differ from the compound which they make. Chlorine is 
a gas of most powerful odor, very suffocating, so that to 
breathe it clear is to die. Sodium is a metal which, if put on your 
tongue, would take fire, and turn into a caustic. Yet this gas and 
metal together form a very mild, pleasant salt, which is a part of 
the food of man and beast every where. 





160 CHLORINE, BLEACHING, AND COMMON SALT, 

Salt-mines. Salt lakes. Salt-springs. How salt is obtained from sea-water. 

Salt is a very abundant article in all parts of the world. There 
are large quantities of it dissolved in sea-water every where. In 
some parts of the world there are vast deposits of solid salt. The 
most famous are those of Poland and Hungary. In the salt- 
mines of Cracow, though salt has been taken from them for over 
six centuries, it is supposed that there is enough still to supply 
the whole world for centuries more. Some parts of these mines 
have been shaped into beautiful forms of various kinds as the salt 
has been taken out. Chapels, halls, etc., have been made, the 
roof being supported by huge pillars of salt. When lighted up 
by lamps and torches the appearance is very splendid. 

Large lakes of very salt water exist in many parts of the earth. 
There is a remarkable one in this country called Great Salt Lake. 
In the northern part of Africa there are some of these lakes, and 
also hills of salt. 

In this country most of our salt is obtained from salt-springs. 
The most noted are those of Salina and Syracuse. In the best 
of the springs there is a bushel of salt in every forty gallons of 
the brine. This is between eight and nine times as much as there 
is usually in sea-water. To get the brine from the springs wells 
are dug, and the brine is pumped up by machinery, and conduct- 
ed by troughs to boilers. Here the water is driven off by heat. 

Sometimes the salt is obtained from the brine by a slower 
process. The brine is exposed to the sun in extensive shallow 
vats, and the water gradually passes off into the air, leaving the 
salt behind. Salt is often obtained in this way, in hot climates, 
from sea- water. 

I will notice here a salt which is called the chlorate of potash. 



CHLORINE, BLEACHING, AND COMMON SALT. 161 

Chlorate of potash. Friction matches. 

If you remember what I told you about the names of salts, you 
can tell by the name of this salt what its composition is. The 
termination ate, you know, always indicates the presence of an 
oxygen acid. The acid in this case is chloric acid, it being chlo- 
rine and oxygen united, and this, with the oxyd of potassium, 
makes chlorate of potash. This salt has a great deal of oxygen 
in it ; hence it is used in obtaining oxygen. It is often put, for 
this purpose, with the oxyd of manganese, from which, you learn- 
ed on page 108, the chemist often gets oxygen. I told you how 
we obtain oxygen from these two substances together on page 18. 
This salt sometimes makes a part of the mixture that is put on 
the ends of friction matches. It makes the phosphorus take fire 
more easily than it otherwise would. Why? Because it gives 
some of its- oxygen to the phosphorus, and thus this substance has 
at once more oxygen than it can get from the air alone, and so 
burns more readily and more briskly. 

Questions. — What other kind of salts is there besides those that you have already 
learned about ? What is the chemical name and composition of common salt ? What 
are the qualities of chlorine ? What is said of its purifying power ? What of its 
odor? What of its bleaching power? Tell about the solution of it. What is the 
use of chlorine in paper-making ? State the difference between grass-bleaching and 
the bleaching with chlorine. What care is required in the latter ? Describe the 
mode of obtaining chlorine represented in Fig. 44. Explain it. Describe and ex- 
plain the experiment represented in Fig. 45. Describe and explain the experiment 
represented in Fig. 46. What is said of the difference between common salt and 
each of its ingredients ? What is said of the abundance of salt ? What of the salt- 
mines of Cracow ? What of salt lakes ? What of the salt obtained in this country ? 
How is the salt obtained from the water containing it? What slower process is 
sometimes employed ? What is said of chlorate of potash ? What of its use in ob- 
taining oxygen gas ? What of its use in making matches ? 

L 



162 CHLORIDES, IODIDES, BROMIDES, AND SEA-WATER. 

A shower of fire. Calomel and corrosive sublimate. 



CHAPTER XXV. 

CHLORIDES, IODIDES, BROMIDES, AND SEA- WATER. 

I HAVE, in the previous chapter, told you about one chloride, 
the chloride of sodium. But there are many other chlorides, for 
chlorine unites with many of the metals. With some it unites 
with such eagerness that they burn together. Thus, if you 
sprinkle a fine powder of the metal antimony into a jar of chlo- 
rine gas, each particle will take fire. You will therefore have a 
shower of fire in the jar, and there will be a white smoke. This 
smoke is composed of very small particles of chloride of antimony, 
for in the burning the chlorine and antimony unite together. 

There are two chlorides of mercury, which are very different 
from each other. One is calomel, and the other is corrosive sub- 
limate. The difference in their composition is that the corrosive 
sublimate has exactly twice as much chlorine in it as the calomel. 
The calomel is called, therefore, the chloride of mercury, while 
the corrosive sublimate is the bichloride. This difference in the 
proportion of chlorine makes a vast difference in the qualities of 
the two substances. The corrosive sublimate is very soluble in 
water, but the calomel will not dissolve at all. The corrosive 
sublimate is a violent eating or corrosive poison, as its name in- 
dicates. If it be swallowed it burns the stomach and all of the 
passage to it. But the calomel is a white powder, like flour, that 
produces no irritation when taken into the mouth. 

Some families keep a bottle of corrosive sublimate, dissolved in 



CHLORIDES, IODIDES, BROMIDES, AND SEA- WATER. 163 

Antidote for corrosive sublimate. Chloride of zinc. Iodine. 

some liquor, as bed-bug poison, for it will kill this and other bugs 
when put upon them. Sometimes, from carelessness, this poison 
has been drank, and many deaths have been caused in this way. 
Now every body ought to know exactly what to do when this 
accident happens, for what is to be done must be done quickly. 
The individual must be made to swallow very freely of the whites 
of eggs. This is the best thing ; but, if there be no eggs at hand, 
milk or flour stirred up in water can be used. 

While chlorine makes with sodium so mild a salt, it forms with 
zinc a very caustic one. The chloride of zinc is used as a caustic 
considerably by surgeons. 

There are many other chlorides, but it would not be interesting 
to you to hear about them. 

There is a great deal of chlorine in the world, but the most of it 
is in the salt-water of the sea, combined with sodium. 

There is another substance, similar to chlorine in many re- 
spects, in sea-water and in sea-plants. It is called iodine. It ex- 
ists in sea- water combined with the metals sodium and potassium, 
as chlorine is combined with sodium. In some sea-plants there is 
Fig. 48. considerable of it, and it is from a ley made with the 
ashes of such plants that it is obtained. 

Iodine is a solid substance, looking something like 
black-lead, but darker in color. If heated it turns into a 
splendid purple vapor or gas, which is one of the heav- 
iest of the gases. If you put a few grains of it in ajar, 
a, Fig. 48, and place the jar in a sand-bath,* 6, warmed 

* A sand-bath is simply fine sand in a dish. The object is to apply the heat grad- 
ually.- This can be done, however, with a spirit-lamp alone, by keeping it at a little 
distance from the glass jar, 




164 CHLORIDES, IODIDES, BROMIDES, AND SEA- WATER. 

Phosphorus and iodine put together. Iodides. Bromine. 

by a spirit lamp, c, the jar will be filled with, the beautiful violet 
vapor. The air that is in the jar, being very much lighter than 
the iodine vapor, is pushed up by it out of the jar. When the jar 
is full of the vapor, place a piece of glass over it, and take it out 
of the bath. 

A taper will burn in this vapor, but not as brightly as in the 
air; but a piece of phosphorus will take fire of itself in it, so eager 
are the iodine and phosphorus to unite together. If some iodine 
Fig^49. be placed in a jar upon a little stand, with a bit of 
dry phosphorus upon it, as represented in Fig. 49, 
they get up so much heat between them that they 
take fire, and a smoke arises. This smoke is partly 
the violet vapor of the iodine and partly the white 
fumes of phosphoric acid ; for the phosphorus, in 
the burning, unites with the oxygen of the air to 
form phosphoric acid, and with the iodine to form iodide of phos- 
phorus. While the acid flies off with the iodine that is turned 
into vapor by the heat, the iodide of phosphorus remains on the 
stand. 

As chlorine forms chlorides with many of the metals, so iodine 
forms iodides with them. The iodide of potassium is a very val- 
uable medicine. Iodine forms two iodides with mercury, one of 
which is of a brilliant scarlet color. The iodide of silver is made 
use of in daguerreotyping. 

There is another very singular substance in sea- water called 
bromine. This is a very heavy, reddish-brown liquid, giving out 
a deep orange-colored fume. The quantity of bromine in sea- 
water is very small. It seems to be quite essential, however, for 




CHLORIDES, IODIDES, BROMIDES, AND SEA-WATER. 165 

A deadly poison. The substances which are in sea-water. 

it is always present. It is also in most salt springs. Wherever 
chlorine is, bromine is along with it. It must be of some use in 
the sea- water, but what we know not. It never exists in the sea- 
water as bromine, but is always in combination with such metals 
as sodium and magnesium, making bromides. The chemist can 
separate it from these. 

This very singular substance is a terrible poison. A single drop 
put in the bill of a bird destroys life at once. One very valuable 
use has been found for it. It is used in photography. 

The three substances of which I have spoken in this and the 
previous chapter, chlorine, iodine, and bromine, are the peculiar 
substances of sea-water. They are always united, however, with 
other substances, making compounds, chlorides, iodides, and bro- 
mides. The reason that the water of the sea has so much of these 
and various other mineral substances in it is, that in the sea are col- 
lected the washings from all kinds of rocks, and sand, and earth. 
The different salts thus collected and dissolved in the sea are 
these : chloride of sodium or common salt, chloride of potassium, 
chloride of calcium, chloride of magnesium, sulphate of lime or 
gypsum, sulphate of magnesia or Epsom salts, carbonate of lime 
or chalk, carbonate of magnesia. These are always present in 
sea-water. Then there are various other substances which are 
more or less present in it. 

We can see of what use some of these substances are in the sea. 
For example, we can see of what use carbonate of lime is. All 
those animals that live in shell houses, as I told you in Chapter 
XXII., need carbonate of lime in the water that they drink, so that 
it may get into their blood, and be used in making their shells. 



166 CHLORIDES, IODIDES, BROMIDES, AND SEA-WATER. 

How saline substances collect in the waters of seas and oceans. 

Most of the solid matter that is dissolved in sea- water is com- 
mon salt. Next to this in quantity are the compounds of mag- 
nesium — the chloride of magnesium and the sulphate and carbon- 
ate of magnesia. It is these that give the bitter taste, especially 
the sulphate of magnesia or Epsom salts. If you have ever taken 
any of this as a medicine you will recognize the resemblance be- 
tween its taste and the bitter taste of sea- water. 

There is a comparatively small amount of these saline matters 
in rivers, because the water in them is always moving on to empty 
into lakes and seas. There is little commonly in lakes, because 
the water is running out of them as constantly as it runs in. 
Thus the water that runs into our great chain of lakes in the 
north runs out through the Eiver St. Lawrence into the Atlantic 
ocean. 

There are some inland seas and lakes that contain more saline 
matters than the ocean itself. This is partly because they have 
no outlet, and are alone by themselves, and partly because there 
is much salt in the neighborhood. The Caspian Sea, the Dead 
Sea, and Lake Aral are of this kind. 

All the saline matters in the water of rivers, and lakes, and seas, 
were once in the rocks of the earth, and were carried off by the 
water which is every where so busy. But, for the most part, be- 
fore this was done, they were in various ways broken off from the 
rocks and ground up, so as to make a part of the earth under our 
feet. Here the water found them, and carried them off into the 
brooks, and rivers, and seas. 

But much of all this is returned, in various ways, from the 
water to the earth again. I will give but one example of this. 



CHLORIDES, IODIDES, BROMIDES, AND SEA-WATER. 



167 



"Water of the Dead Sea very heavy. 



Experiment. 



The coral animals, that I told you about in Chapter XXII., tak- 
ing the carbonate of lime which the earth has supplied to the 
water, give it back to the earth in reefs, and islands, and penin- 
sulas. 

The more salt there is in water the heavier it is, and the more 
will it bear up solid substances. Thus a man floating in common 
water only has a part of his head above the surface, but in the 
water of the Dead Sea it costs him no effort to keep breast high 
in it. A ship there would easily carry a load which would sink 
it if in water almost any where else. 



Fig. 50. 




There are some pretty experiments 
which show the difference between salt 
and fresh water in regard to floating 
substances. Suppose that you have an 
egg in a jar half full of water. The egg 
will be at the bottom of the jar, for it 
is heavier than water. Pour now some 
strong brine into the bottom of the jar 
through a long tube, as represented in 
Fig. 50. The brine will force up the 
lighter water, and with it the egg. The 
egg will remain at the middle part of 
the jar, at the bottom of the fresh water, 
floating on the brine, just as a piece of 
wood would float on the surface of water 
in the jar, at the bottom of the air, if the 
jar were half full of water, air of course 
being above it. 



168 CHLORIDES, IODIDES, BROMIDES, AND SEA- WATER. 

Experiment. 



Fi s- 51 - A very pretty 

experiment is rep- 
resented in Fig. 51. 
The jar A is filled 
with brine. A lit- 
tle toy ship is float- 
ing upon it. To 
have the experi- 
ment succeed, the 
ship must be so 
loaded that it will 
just float upon the 
brine. If now you 
place the ship in 
the jar of fresh wa- 
ter, B, it will sink. 

Questions. — What substances are formed by the union of chlorine with metals? 
What is remarked about this union in some cases ? What is said about the two chlo- 
rides of mercury ? What about poisoning with corrosive sublimate, and the anti- 
dote ? What is said of the chloride of zinc ? Where is most of the chlorine that is 
in the world ? Where is iodine found, and in combination with what ? Describe 
this substance. Explain Fig. 48. State what is represented in Fig. 49, and explain 
it. What are iodides, and what is said of some of them ? Describe bromine. What 
is said of the quantity of it in sea-water? With what is it united? What is said of 
its poisonous character? To what use has it been applied? What is said of the 
three substances peculiar to sea-water ? What are the solid substances that sea-water 
has deposited in it ? Of what use is the carbonate of lime in sea-water ? What is said 
of common salt ? What is the cause of the bitter taste of sea- water ? What is said 
of solid matters in the water of rivers and lakes ? Mention some inland lakes and 
seas that are salt. Why are they so ? Give the experiment with the egg. Also the 
experiment with the toy ship. 




SOLUTION AND CRYSTALLIZATION. 169 

Differences in the solubility of substances. Potash and lime contrasted. 



CHAPTER XXYI. 

SOLUTION AND CRYSTALLIZATION. 

There is a great difference in the different oxyds and salts in 
regard to being dissolved. Some of them will not dissolve at all, 
some sparingly, and water will take in large quantities of some 
others. Calomel, for example, which is a chloride of mercury, is 
perfectly insoluble ; that is, not a particle of it can be dissolved in 
water. But corrosive sublimate, the bichloride of mercury, is very 
soluble. Magnesia, an oxyd of the metal magnesium, is insoluble. 
You know this if you have ever taken calcined magnesia, as it is 
called, stirred up in sugar and water. But potash, which is an 
oxyd also, is exceedingly soluble. It is very eager for water, and 
if exposed will become dissolved in the water which it gathers 
from the air. It can be dissolved in half of its weight of water ; 
that is, a pound of water will dissolve two pounds of potash. Now 
lime, which is another oxyd, likes water, but it takes a thousand 
pounds of water to dissolve one pound of lime. 

The Creator has made this great difference between potash and 
lime, in regard to solubility, because the difference is needed. For 
example, we want to use lime in plastering walls ; but it would 
not answer for this if it would, like potash, gather water from the 
air and dissolve in it. It would be rather inconvenient to have 
the plastering in our houses dissolve and run down whenever it 
chanced to get wet. But for the uses for which man needs potash 



170 SOLUTION AND CRYSTALLIZATION. 

Solubility of salt. Carbonate of lime and of soda contrasted. 

it is well to have it dissolve easily. For instance, it is used in mak- 
ing soap, and needs to be soluble for this purpose. 

Salt dissolves easily, but not as easily as potash does. It would 
be inconvenient to have it do so. We want to keep salt dry for 
use, and this we could not do if it were as fond of water as pot- 
ash is. The Creator has made it soluble to just the right degree 
to suit the uses for which he designed it. It sometimes troubles 
us by gathering moisture from the air, but this is only when the 
weather is damp ; that is, when the air has much water in it. 

Let us compare two carbonates in regard to solubility, the car- 
bonate of soda and the carbonate of lime. The carbonate of soda 
is very soluble. This is convenient for the uses to which man puts 
this salt. But the carbonate of lime, which appears in the forms 
of chalk, limestome, marble, etc., is very sparingly soluble. It 
would be bad to have it dissolve readily in water. This salt, you 
know, makes the shells of oysters and other shell-fish. It would 
not be well to have their shell houses made of a material that the 
water could dissolve easily. And yet, if carbonate of lime were 
not somewhat soluble, how could it get into the blood of these 
animals so that it can be made into shell ? You see, then, that the 
Creator has made this all just right. 

But, besides this, it would be very injurious to have so much 
carbonate of lime in the water as there would be if it were very 
soluble. The rain that comes down upon chalk and limestone, 
which here and there form rocks and hills, and even mountains, 
washes down always a little, and carries it among the particles of 
the earth, and down streams into the ocean. That little is enough 
for building the houses of the shelled animals and other purposes. 



SOLUTION AND CRYSTALLIZATION. 171 

Silica. Saturation. What it is to dissolve a substance. 

If the carbonate of lime were more soluble there would be more 
than enough, and it would give us a great deal of trouble. When 
well-water is hard it is very commonly because there happens to 
be- considerable carbonate of lime in it. 

Silica is, like carbonate of lime, sparingly soluble. Suppose 
that it were not soluble at all ; all our grass and grain would lie 
flat along the ground, for it is the silica in them that gives them 
the firmness by which they stand up. 

Commonly, when a substance is soluble, there will more dissolve 
in hot than in cold water, but this is not so with common salt. 

When we have made water dissolve just as much of a substance 
as it can, we call it a saturated solution. This word comes from a 
Latin word which signifies to satisfy or feed to the full. Water 
is more easily satisfied or saturated with some substances than 
with others. Potash and lime are in strong contrast in this re- 
spect ; a half a pound of water will not be satisfied till it has dis- 
solved a pound of potash, while a thousand pounds of water will 
be satisfied or saturated with a pound of lime ; that is, it takes two 
thousand times as much potash to saturate water as it does lime. 

Observe what it is to have a solid substance dissolved in water. 
Some solid substances you can mix up very thoroughly with wa- 
ter by powdering them well, and yet they do not dissolve. Cal- 
cined magnesia is readily mixed with water, but it is not dissolved, 
and it settles after the water has stood for a little while. But a 
substance that dissolves disappears. You can not see it. If it 
have color, you see that in the water, but not the little grains or 
particles, as you do in the magnesia and water. A perfect solu- 
tion is clear and transparent. The substance dissolved is much 



172 SOLUTION AND CRYSTALLIZATION. 

Water dissolved in air. Crystallization of alum. 

more finely divided up than when it is merely mixed in the wa- 
ter ; and if the solution be left to stand, the solid substance re- 
mains, as we may say, hidden among the particles of the water. 
None of it settles unless some of the water is evaporated ; and 
the more the water evaporates, or flies off into the air, the more 
will the dissolved substance settle. If the substance dissolved 
be a colored substance, it colors the fluid uniformly through- 
out, the minute particles of it being diffused every where in the 
fluid. 

As water dissolves solids, so air dissolves water. In the clear- 
est day, when the air appears to us to be dry, there is a great deal 
of water in the air ; you do not see it for the same reason that 
you do not see a solid substance when it is dissolved in water. 
The water is dissolved in the air ; and hot air will dissolve more 
water than cold, just as hot water will dissolve more alum than 
cold water. When water gathers on our cool tumblers in hot 
weather, it is because the hot air all around the tumblers has so 
much water dissolved in it. 

As crystals are often formed from solutions, it is proper to speak 
here of crystallization. 

Hot water will dissolve twice as much alum as cold water. If 
you dissolve, then, as much as you can of alum in hot water, that 
is, make a saturated solution, when the water becomes cold half 
of the alum will become solid again ; and in doing so it will gather 
in crystals upon the bottom and sides of the vessel. If you sus- 
pend a wire in the vessel of dissolved alum, as it cools the crys- 
tals will collect upon this wire. You have, perhaps, seen baskets 
made of alum or other crystals. They were made in this way : 



SOLUTION AND CRYSTALLIZATION. 173 

Wonders of crystallization seen in ice and snow. 

the basket, made of bonnet-wire, was suspended in a hot solution 
of alum, and the crystals formed upon all parts of the wire. 

When the substance used dissolves as freely in cold as in hot 
water, as is the case with common salt, crystallization is produced 
only by evaporation. As the water goes off into the air the crys- 
tals form. 

How beautiful and curious a process crystallization is ! In what 
exact order are the particles arranged to make such very smooth 
surfaces and such straight edges ! They are particles, remember, 
that are so small that we can not see them even with a powerful 
microscope ; and yet, in making a crystal, each one is made by the 
Creator to take its right place. Sometimes this arrangement of 
the particles is very quickly done. The most familiar example we 
have of this is in water. Sometimes, on taking up a pitcher of 
water in a cold morning, a great part of the water turns all at once 
into crystals, which shoot across in the pitcher in every direction. 
If you pour out what water remains fluid, you can see the crys- 
tals. The explanation of the phenomenon is easy. The water in 
the pitcher during the night became freezing cold, but it was per- 
fectly still, and so the particles of the water remained just so; but 
the shaking given to them by taking up the pitcher makes them 
arrange themselves in the solid crystalline form. 

We have the safp quick formation of crystals, on a large scale, 
in every snow-storm. The clouds are the reservoirs of water 
from which the snow is made, the water in them being in the 
form of fog ; and the particles of this fog are in a snow-storm 
continually arranging themselves in crystals, and so fall to the 
earth. 



174 



SOLUTION AND CRYSTALLIZATION. 



Crystals of mica, salt, Iceland spar, gypsum, and water. 





There are great varieties in crystalline arrangement. I will 
Fig. 52. point out some of them. In Fig. 52 you have repre- 
sented a lump of mica. This is arranged in leaves 
which you can peel off exceedingly thin. You see this 
mineral used for windows in stove doors. The sheets 
of mica, or isinglass, as it is commonly called, used for 
this purpose, are really made up of very many of these 
thin leaves. In Fig. Fig 53> Fig 54 

53 you see the shapes 
of the crj^stals of common salt. 
They are exactly square blocks. 
And in Fig. 54 you see the forms 
of the crystals of a very beauti- 
ful mineral called calc spar, or 
sometimes Iceland spar, because it was first brought from Iceland. 
It is composed of the same things as common chalk. You see 
that the crystals are not square like those of salt, but they are 
sloping. These are but three of the very many varieties that oc- 
cur in the shapes of crystals. Sometimes the same substance^ap- 
pears in many different forms. This is the case with gypsum, as 
noticed on page 137. The various forms and arrangements of 
the crystals of water in snow and frost are very beautiful. I 
have spoken of them particularly in the chajg^ on Snow, Frost, 
and Ice, in the Third Part of the Child's BooE^f Nature. 

In the crystals of some salts there is water locked up and con- 
cealed, but in some there is none. In carbonate of lime there is 
no water, but only carbonic acid and lime. In carbonate of soda, 
on the other hand, there is more of water than there is of carbonic 



SOLUTION AND CRYSTALLIZATION. 175 

Water of crystallization. Gunpowder. Deliquescing and efflorescing. 

acid and soda together. In 100 pounds of this salt there are 63 
of water. Yet the crystals are dry crystals ; for the water is a 
part of the solid substance, locked up with the carbonic acid and 
the soda. You can get this salt without any water in it by heat- 
ing it ; but the first thing it does on applying the heat is to melt 
in its own water. As you continue the heat you drive off this 
water into the air, and the powder of the salt is left behind. It 
is no longer crystalline ; for it can not be so without its supply 
of water, or its water of crystallization, as the chemists express it. 
When this term is used in regard to any substance, we mean the 
amount of water which is contained by it when it is in a crystal- 
line form. This differs in different substances. Some require 
no water, some a little, and some a good deal. 

Nitrate of potash, or saltpetre, has no water in it. If it had, it 
might not answer as well for making gunpowder. Nitrate of 
soda has no water in it, and it would do for making gunpowder 
as well as the nitrate of potash, were it not for one thing : it gath- 
ers moisture from the air. This would not answer for powder, 
for powder must be kept dry, you know. A salt which thus 
gathers moisture from the air is said to deliquesce — a word which 
comes from a Latin word meaning to melt. A salt, on the other 
hand, which, on exposure, loses its water of crystallization, and 
changes from a crystal into a powder, is said to effloresce. Crys- 
tals that do this have a mealy powder gradually form on their 
surface. The word effloresce comes from the Latin word mean- 
ing to flower. It is as if the mineral flowered out. 

Many of the metals show us crystals. In the formation of the 
lead-tree described on page 142, the lead becomes crystalline. 



176 SOLUTION AND CRYSTALLIZATION. 

Cry of tin. Tin crystals. 

The tree is made of crystal joined to crystal. If you bend a bar 
of tin it gives a peculiar sound, which has been called the cry of 
tin. This is supposed to be produced by the rubbing of the little 
crystals of which the metal is composed upon each other. You 
can see the crystals of tin beautifully developed by a very simple 
process. Take a piece of ordinary tin, and heat it over a lamp 
till the coating of tin melts ; then let it cool quickly, and wash 
the surface with a little aqua regia, the acid mixture mentioned 
on page 123. 

Questions. — What is said of the difference in solubility of different oxyds and 
salts ? Give some illustrations. Show the necessity for the difference in regard to 
lime and potash. What is said of the solubility of common salt ? What of the sol- 
ubility of carbonate of soda and carbonate of lime ? What would be the difficulty 
with the shell-fishes if carbonate of lime were very soluble ? Why is it necessary for 
them that it should be a little soluble ? How does carbonate of lime get into the 
sea ? What is one of the causes of the hardness of well-water ? What is said of 
silica ? What is said of hot and cold water in dissolving substances ? What is a 
saturated solution ? State the difference between potash and lime in saturating wa- 
ter. Explain what solution really is. What is said of the solution of water in air ? 
What of making crystals of alum ? What of making crystals of common salt ? 
What is said of the process of crystallization ? State the example given of sudden 
crystallization. What is said of crystallization in a snow-storm ? Describe the three 
varieties of crystalline forms that are given. What is said of the same substance 
appearing in various forms ? Give in full what is said of the water of crystallization. 
What is said of nitrate of potash and nitrate of soda ? What is deliquescence ? 
What is efflorescence ? What is said of crystals in metals ? What is said about tin ? 



CHEMICAL AFFINITY. 177 

What chemical affinity is. Potassium and iron contrasted. 



CHAPTEE XXVII. 

CHEMICAL AFFINITY. 

I have told you considerable about chemical affinity, but we 
will now look at the subject a little more particularly. 

As you have already learned, when one substance has a dispo- 
sition to unite with another, it is said to have an affinity for it, 
or the two substances are said to have an affinity for each other. 
Sometimes one expression is used, and sometimes the other. 

The strength of the liking or affinity is very different in dif- 
ferent cases. I will illustrate this. Iron and oxygen have an 
affinity for each other, but it is not very strong, and, therefore, it 
works slowly. It takes time, you know, for iron exposed to the 
air to rust. Now look at the metal potassium in contrast with 
this. As soon as it is exposed to the air the oxygen begins to 
unite with it. It tarnishes at once, and soon it is all turned into 
potash ; that is, the oxygen of the air has united with the whole 
of the metal. So ready is potassium to unite with oxygen, that 
if it be thrown upon water it takes the oxygen away from the 
hydrogen ; and it does this so quickly that it gets up a confla- 
gration of the hydrogen. Even the coldness of ice will not pre- 
vent this. If the potassium be thrown upon ice, it will even then 
take the oxygen out of the cold embrace of hydrogen, and burn 
up the hydrogen too. 

But iron and oxygen do not always unite slowly. Introduce 
them to each other in a very hot place, and they will be quick 

M 



178 CHEMICAL AFFINITY. 



Affinity of iron for oxygen affected by heat. The noble metals. 

enough in uniting. You have seen this in burning iron or steel 
in oxygen gas. If you put the iron into the oxygen without get- 
ting up considerable heat, they will not unite. But make the 
heat by having something on fire at the end of the steel-wire, and 
now the wire will burn, because the heat that is begun by the 
burning at the end of the wire will be kept up by the uniting of 
the wire with the oxygen. This would not be so if the wire were 
in common air, because the oxygen would not come fast enough. 
When you strike fire with your heel as you walk, the fire does 
not keep burning on the heel, because there is not enough oxygen 
for this. The heat produced by the blow only makes the single 
little particle burn as it flies off. The fire goes out as quickly as 
it is made. 

In one of the ways of obtaining hydrogen, as described on page 
62, we see how the affinity of iron for oxygen is increased by 
heat. As the steam, that is, the vaporized water, passes among the 
bits of iron, the iron takes away the oxygen from the hydrogen 
at once, and lets the hydrogen go on alone. It takes the oxygen 
very quickly ; but observe that it does not set fire to the hydro- 
gen, as the potassium does when it takes oxygen from hydrogen, 
as it is thrown upon water. 

What are called the noble metals — gold, silver, mercury, and 
platinum — have almost no affinity for oxygen. Not even heat 
can make them oxydize. You may expose gold to the hottest 
fire, and the oxygen will not unite with it. It can be made to 
unite with it, but it does not like to remain in its company. 
Light even will separate it from the gold ; or, in other words, the 
oxyd of gold is decomposed by light. If mercury be heated very 



CHEMICAL AFFINITY. 179 



Phosphorus and oxygen. Influence of heat on affinity. 

hot, it will fly off into the air, finely divided up as vapor, but it 
will not unite with the oxygen that is in the air. 

I have told you, in Chapter IY., how hard it is to make oxy- 
gen and nitrogen unite together, and have given there some rea- 
sons why the Creator ordained that it should be so. 

The affinity of phosphorus and oxygen for each other is so 
great, that a little quick rubbing of a match that has phosphorus 
on the end of it will set it on fire. The phosphorus on the match 
is not alone, but is mixed with other substances. In this mixture 
there is very commonly chlorate of potash, a salt that I told you 
about on page 161. There is a plenty of oxygen in this, and why 
it is put with the phosphorus I have already told you. 

While heat sometimes operates in favor of chemical affinity, it 
sometimes operates against it, and then it tends to produce de- 
composition. In carbonate of lime we have carbonic acid and 
lime united together by chemical affinity ; but apply great heat 
to it, as stated on page 131, and the hold of the acid and the lime 
upon each other will be broken up. The carbonic acid will fly 
off in the air, leaving the lime alone. The heat in this case, act- 
ing against affinity, decomposes the salt. 

But heat will not drive off the carbonic acid from carbonate of 
potash. To do this, you must introduce another acid that has a 
stronger affinity for the potash than the carbonic acid has. Acetic 
acid will do it, as you saw in the experiment noticed on page 132. 
Tartaric acid will also do it. 

When we want a good deal of carbonic acid gas for certain 
purposes, we use the bicarbonate of potash, commonly called sal 
aeratus. This has twice as much carbonic acid as the common 



180 CHEMICAL AFFINITY. 

Hotv affinity is affected by solution. 

carbonate has. People often use this in making bread and cake, 
introducing some acid to take the potash, that the carbonic acid 
gas may be set free and raise the dough. Sour milk is often em- 
ployed to decompose thus the sal asratus. 

"When we separate carbonic acid from carbonate of lime by 
heat, very great heat is required. But we can get it away with- 
out any heat at all. It is by using an acid which has a stronger 
affinity for lime than the carbonic acid has. This is illustrated in 
the mode of obtaining carbonic acid gas described on page 37. 
The muriatic acid takes the lime and lets the carbonic acid go. 
The same thing can be done with sulphuric acid, for this has a 
greater affinity for lime than carbonic acid has. 

Solid substances need commonly the help of water to make 
their affinities for each other operate. If you mix the two pow- 
ders, tartaric acid and bicarbonate of soda, together dry, there will 
be no action ; but if you dissolve them, as stated on page 134, as 
soon as the solutions are mixed the tartaric acid at once takes 
hold of the soda, and the carbonic acid, thus released from the 
soda, effervesces. So, too, if you make a heap of the two pow- 
ders mixed together, all will be quiet ; but pour some water on 
the heap, and there will be a great disturbance as the water intro- 
duces the tartaric acid to the soda, and the carbonic acid has no- 
tice to quit. Why the difference ? It is because in the dry state 
the two kinds of particles do not get near enough to each other 
to produce the effect. Powders, even when made very fine, look 
coarse when examined by the microscope ; but the same sub- 
stances dissolved in water are much more minutely divided, and 
so their particles are more thoroughly mixed up, and are nearer 
to each other. 



CHEMICAL AFFINITY. 



181 



Heat produced by affinity. 



A curious example. 



You have seen that heat sometimes favors chemical affinity, 
and sometimes acts against it. Besides this, heat is often caused 
by chemical affinity. Generally, when any thing is burned, the 
heat which is produced is owing to the rapid union of oxygen 
with the burning substance. Thus, if carbon is burned, the car- 
bon unites with oxygen, and so makes heat. The heat here 
comes from the affinity of carbon and oxygen for each other. 
So, when water and lime are mixed together, as in the making of 



Fig. 55. 




mortar, great heat is pro- 
duced by the action of the 
affinity. Sulphuric acid 
and water have a strong 
affinity for each other, and, 
as stated on page 119, 
when they are mingled to- 
gether considerable heat 
is caused. In Fig. 55 you 
see represented a curious 
way of using this heat. 
Two men, who have gone 
up in a balloon so high 
that it is very cold, are 
hugging a bottle in which 
they have just mixed some 
sulphuric acid and water. 
It is supposed that the 
heat in this case is owing 
to a good squeezing which 



182 CHEMICAL AFFINITY. 

Regularity of chemical proportions. Compounds of oxygen and nitrogen. 

the acid gives to the water, or which, they give to each other. 
For if a pint of acid and a pint of water be poured together, the 
two pints make less than a quart ; and this sudden condensation 
is supposed to create the heat. 

Chemical affinity is exceedingly regular in its operations. It 
does not make substances unite in all sorts of proportions. If 
two substances unite together to form several different compounds, 
the proportions are so regular that they can be represented by 
whole numbers. I have already told you about this in regard to 
some compounds. For example, the bicarbonate of soda has ex- 
actly twice as much carbonic acid in it as the carbonate has (page 
134), and the bichloride of mercury has twice as much chlorine 
as the chloride. So, too, in the five compounds of oxygen and 
nitrogen (page 29), the proportions of oxygen are exactly as 1, 
2, 3, 4, and 5. 

Observe now, in regard to the compounds of oxygen and nitro- 
gen, that the nitrogen is the same in amount in all of them. 
The difference of proportion is only in the oxygen. Of the five 
compounds there is the most oxygen in the nitric acid, and the 
least in the nitrous oxyd or laughing gas. In the nitrous oxyd 
the proportion of oxygen is as 8 to 14 ; that is, in 22 pounds of 
nitrous oxyd there are 8 of oxygen and 14 of nitrogen. But as 
in nitric acid there is the same amount of nitrogen, but five times 
as much oxygen, the proportion of oxygen to nitrogen in this 
acid is as 40 to 14 ; that is, while there are 8 pounds of oxygen 
and 14 of nitrogen in 22 of nitrous oxyd, there are 40 of oxygen 
and only 14 of nitrogen in 54 of nitric acid. Can you tell me, 
then, how much there is of oxygen and of "nitrogen in 108 pounds 



CHEMICAL AFFINITY. 183 

Some of the arithmetic of chemistry. Difference between compounds and mixtures. 

of nitric acid ? If you work out the following sums by the rule 
of three, you will get the right answers. 

54 : 40 : : 108 : amount of the oxygen. 
54 : 14 : : 108 : amount of the nitrogen. 

The proportions of the different compounds of oxygen and ni- 
trogen may be stated thus : 

Nitrogen. Oxygen. 

Nitrous oxyd 14 8 

Nitric oxyd 14 16 

Hyponitrous acid 14 24 

Nitrous acid 14 32 

Nitric acid 14 40 

The difference in the proportion of oxygen, you see, is exactly 
as 1, 2, 3, 4, and 5. There is never the least variation from this. 
You can not in any way make, for example, 8-J pounds of oxy- 
gen unite with 14 of nitrogen. The extra half pound will be put 
one side. The 14 pounds of nitrogen will not take a jot more 
than 8 of oxygen. To make it unite with any more, you must 
give it twice as much, 16 pounds, and then it will make nitric 
oxyd ; or 24, and then it will make hyponitrous acid, and so on. 

There are some substances that unite in a different range of 
proportions — 1, 1-J, 2, 3, 3|-. But this can not be really called an 
irregularity. 

Compounds differ from mere mixtures in these fixed and defi- 
nite proportions. You can mix alcohol and water together in all 
kinds of proportions. The same is true of the mixtures of the 
metals called alloys ; but in forming real compounds, substances 
unite together in exact proportions. 



184 CHEMICAL AFFINITY. 



The order preserved in creation. 



We see in this exactness of proportions, as we do in crystalli- 
zation, what order prevails in creation. Nothing is left loose and 
indefinite, as is too often the case with many of the arrangements 
of man. Amid all the changes of matter, whether taking place 
in quiet, or in the agitation of combustion, or even explosion, 
there is always in the combinations that occur a strict compli- 
ance with the arithmetical proportions that I have indicated. 
God thus marshals in perfect order alike minute particles and 
immense worlds. 

Questions. — What is chemical affinity? State the difference in strength of affin- 
ity of iron and potassium for oxygen. What is said of the quick union of iron with 
oxygen ? How is the affinity of iron for oxygen illustrated in one mode of obtain- 
ing hydrogen ? What is said of the noble metals ? Give what is stated in Chapter 
IV. about the union of nitrogen and oxygen. What is said of the affinity of phos- 
phorus for oxygen ? What is the object of putting chlorate of potash with phos- 
phorus in matches ? Give an example of heat acting in opposition to chemical affin- 
ity. What is said of decomposing carbonate of potash ? What is decomposition ? 
What is said of the bicarbonate of potash ? What is said of separating carbonic 
acid from carbonate of lime ? What is said of the influence of water on chemical af- 
finity? State what is said about mixing soda powders. Give some examples of heat 
being produced by chemical affinity. Explain Fig. 55. What really produces the 
heat in this case ? What is said of the regularity with which chemical affinity acts ? 
State particularly what is said of the compounds of nitrogen and oxygen. How much 
oxygen and how much nitrogen is there in 108 pounds of nitric acid ? How much 
in 162 pounds ? How much in 100 ? in 60 ? in 25 ? State what is said about the 
exactness of the proportions of oxygen in the different compounds of oxygen and 
nitrogen. What different range of proportions is there in some cases ? How do 
compounds differ from mixtures in regard to proportions ? What is said of the or- 
der preserved in creation ? 



wood. 185 



The chemistry of life. Composition of -wood. 



CHAPTER XXVIII. 

WOOD. 

So far I have told you mostly about the chemistry of mineral 
substances ; that is, substances which neither have life in them 
nor are produced by the operations of life. Most people, when 
the term mineral substances is used, think only of solid substances ; 
but air and water are as really minerals as the crystals you see in 
a cabinet of minerals, or the rocks and stones that you see about 
you. Wood, sugar, starch, gum, skin, flesh, etc., on the other 
hand, are not mineral, for some of these have life, and all of them 
are produced only by the operations of life in either vegetables 
or animals. It is to this chemistry of life, as we may call it, that 
we shall attend in the few remaining chapters. I shall begin with 
the chemistry of vegetables. 

I have told you already something about the chemistry of vege- 
tables in speaking of carbon as entering into the leaves and mak- 
ing a part of the wood of trees. Now wood is composed of three 
things, carbon, oxygen, and hydrogen. You see that it is com- 
posed of a solid united with two gases. When we make charcoal 
out of wood, as I described to you on page 33, we decompose the 
wood. We send off its oxygen and hydrogen into the air by the 
heat of the burning, and most of the carbon is left behind alone. 
I say most of it, but not all, for some of the carbon unites with 
the oxygen in the combustion, and flies off as carbonic acid gas. 

Though you can thus decompose wood, you can not take the 



186 wood. 

Man can not make wood. A contrast. How wood is made. 

ingredients and unite them together so as to make wood of them. 
If you mix up powdered charcoal with water, you have all of the 
ingredients of wood together ; but you can not in any way make 
them unite together to form wood. So you have the ingredients 
of wood if you put charcoal into a jar filled with oxygen and hy- 
drogen gases, but they will not turn into wood ; they will remain 
just so. If you light up the charcoal before you put it into the 
jar, an effect will be produced, but no wood will be made ; an ex- 
plosion will take place, the oxygen and hydrogen uniting together 
in a great hurry, forming water, and some of the oxygen uniting 
with the charcoal to form carbonic acid gas. So, again, if you 
take carbonic acid gas and mingle it in a jar with hydrogen gas, 
you have the three ingredients of wood, carbon, oxygen, and hy- 
drogen, but they will not unite to make wood. 

See how different this is from what we can do with some of the 
minerals that I have told you about. For example, take sulphate 
of copper or blue vitriol : this is composed of three things, sul- 
phur, oxygen, and copper. Now W€ can make the sulphur and 
oxygen unite to form sulphuric acid, and then this acid will unite 
with the copper, forming the sulphate of copper. How readily, 
as another example, carbon and oxygen unite, and make carbonic 
acid, and then the acid unites with the lime to form the carbon- 
ate, chalk. 

But, although we can not in any way make the ingredients of 
wood unite to form wood, it is done in the tree. Let us see how. 
Much of the carbon is furnished from the air, being taken in by 
the leaves from the air, as you learned in Chapter VIII. Then 
the water that comes up in the sap from the roots furnishes the 



wood. 187 

Varieties of wood. A comparison. 

oxygen and hydrogen, for water, you know, is composed of these 
two gases. We may say, then, that the tree makes its own wood 
out of charcoal and water. 

Wood in every tree is composed of the same things, carbon, 
oxygen, and hydrogen, although the trees are so "different ; and 
there is more difference in the ways in which wood is put togeth- 
er in different trees than you would suppose from looking at the 
outside, or from seeing the wood itself with the naked eye. The 
microscope shows astonishing differences. In order to see these, 
exceedingly thin shavings, of various kinds of wood, are cut with 
a very sharp instrument across the grain of the wood. On ex- 
amining these with the microscope, they are so much magnified 
that we can see just how each kind of wood is put together. In 
some, as the pine, there is a very open network, with here and 
there large round openings, while in other more solid woods the 
spaces are much less. These spaces have very great variety of 
arrangement in different kinds of wood, and in some the arrange- 
ment is exceedingly beautiful. 

Bearing in mind the fact that in all these varieties we have 
really the same thing in composition, is there any thing that you 
can remember of what I have told you that is somewhat like 
this? Can you recollect any mineral substance that appears in 
various forms, and yet in composition is the same in all these 
forms, as the wood is in its forms? I will mention one, gypsum, 
noticed on page 137, and perhaps you can remember some others. 

But there is still more variety in wood than I have yet told 
you about. There are a great many other things which are real- 
ly wood besides those which people commonly call by this name. 



188 wood. 

Bark, leaves, flowers, stalks, etc., are different forms of wood. 

The bark of trees is wood, only in a different form from the wood 
which it covers, very much as chalk or the common limestone 
differs from marble. Hold a leaf up so that the light can shine 
through it. All that delicate frame-work that you see is .a 
wooden frame-work. More than this, the skin of the leaf and all 
its filling up are wood. The whole leaf is wood except the sap 
that is in it, and that which gives it its beautiful color ; and what 
I have said of leaves is true also of flowers. The most delicate 
flower that you can find is made of wood — very, very fine and 
delicate is such wood, and yet it is wood. 

You see a hyacinth growing at the window in a glass vessel 
in which there is nothing but water. The plant that grows up 
from the hyacinth bulb is little else than wood filled out in all 
its cells with water. See how this wood is formed. The water 
furnishes the oxygen and hydrogen, and the carbon comes from 
the air. 

Every stalk of grain and spire of grass is made mostly of wood. 
In both of these cases we have fine particles of flint scattered all 
along in the wood to make it firm enough to stand up in spite of 
the wind. 

Much of the clothing that you wear is nothing but wood. You 
can hardly believe this ; but so it is. A shirt, whether it be 
made of cotton or linen, is a wooden shirt. Cotton or linen fibre 
is woody fibre. It is composed of carbon/oxygen, and hydrogen 
in exactly the same proportions with what we commonly call 
wood. 

You remember that I told you in a previous chapter about the 
old-fashioned tinder-box, Charred or scorched linen was always 



wood. 189 

Paper is wood. Wooden partitions in fruits. Wooden bottles in oranges. 

kept in the box to catch the spark from the steel. This is really 
charcoal, made from the linen, just as we make charcoal from 
sticks of wood — that is, by a partial burning. It was used for 
this purpose instead of common charcoal because it is so fine in 
its division into fibres that the spark very readily sets fire to it. 

All paper is wood. It is made, when it is fine, as writing-pa- 
per, of cotton and linen rags, and these are wood. If you tear a 
piece of letter-paper, and look at the torn edge through a magni- 
fying glass or a microscope, you will see very plainly the woody 
fibres pointing out in all directions from the edge. In paper these 
fibres^ are not regularly arranged as in the cotton after it is gath- 
ered, but they are mingled together in all sorts of ways, lying 
across each other in confusion. 

All the frame-work, as we may call it, of fruits is wood. All 
the partitions in fruits are wooden partitions. The orange, you 
know, is divided into several parts by partitions. These are 
made of wood. Besides this, the juice of an orange is inclosed in 
thousands and thousands of little bottles, and these bottles are 
wooden bottles. The next time you eat an orange, observe them. 
See how pretty they are, and how nicely they are packed in each 
of the parts of the orange. Their large rounded ends are toward 
the peal, and their slender pointed ends are toward the middle of 
the orange. "When you eat an orange you crush a multitude of 
these wooden bottles, and the juice runs out of them into your 
mouth. And so, when you eat any juicy fruit, you break up 
wooden apartments or cells that hold the fluid. Even in the 
most juicy fruits there is some wood all through them, and the 
skins or coverings of the fruits are made of wood, 



190 WOOD. 

"Wooden coverings of seeds. A comparison. 

The coverings of all seeds are wooden. In some of the nuts 
the woody substance forming their covering is very dense and 
hard, as in the cocoanut, the walnut. The substance called veg- 
etable ivory is wood very closely put together. 

The very delicate forms in which woody substance sometimes 
appears remind us of the fine crystals in which some minerals 
sometimes show themselves. Thus saltpetre, which is commonly 
rather a coarse-looking mineral, is sometimes seen on the walls of 
caverns in fine, needle-like crystals ; and, to take another exam- 
ple of a more familiar character, the delicate tracing of the frost 
on our windows is but another form or arrangement of the same 
material that we have in thick ice. 

Questions. — What is the difference between substances which are mineral and those 
which are not ? What have you already learned about the chemistry of vegetables ? 
What is said about the composition of wood ? What is done to wood in making 
charcoal ? What is said about making wood ? Give the contrast to this in regard 
to minerals. How is wood formed in the tree ? What is said of the different forms 
of wood in different kinds of trees ? Give the comparison in relation to this. What 
is said of leaves and flowers ? What of the hyacinth ? What of grain and grass ? 
What of clothing ? What of tinder ? What of paper ? What of fruits ? Describe 
the arrangement of the orange. What is said of the coverings of seeds ? What is 
vegetable ivory ? Give the comparison in relation to the delicate forms of wood. 



STARCH AND SUGAR. 191 



Starch in the vegetables that we eat. How to obtain it from flour. 



CHAPTER XXIX. 

STARCH AND SUGAR. 

Starch is a very common substance in vegetables. It is not 
so common as wood, for that, as you have seen, is every where, in 
every part of all vegetables, from the largest trees to the smallest 
plants. There is some starch in all the vegetable substances that 
we eat. In some kinds there is a great deal of starch. Four fifths 
of the flour of which our bread is made is starch. Most of the 
potato is starch. There is much of it in chestnuts, and even in 
horse-chestnuts it constitutes one eighth of the whole. Arrow- 
root is a starchy meal, prepared from some plants that grow in 
marshy grounds in warm climates, as the East and West Indies. 
Sago is a starchy substance, prepared from the pith of various 
kinds of palm-trees. From all this you see that a large part of 
the food of man is starch. 

You can very readily obtain starch from wheat flour. Moisten 
a handful of it with enough water to make a thin paste. Put this 
into a piece of thick linen cloth and knead it, adding water to the 
paste as long as the liquid which runs through the cloth appears 
milky. Let the liquid in the vessel stand for some time, and a 
white powder will settle at the bottom. This is wheat starch. 
What remains in the cloth I will tell you about in the next 
chapter. 

The starch is in grains, and each little grain, as seen by the mi- 
croscope, has a covering. Now in boiling starch we swell it up 



192 STARCH AND SUGAR. 



Composition of starch. Sources of sugar. How sugar is made in plants. 

into a thick jelly. In this operation the coatings of the grains are 
broken, and the starch absorbs considerable water. This is the 
reason that rice, beans, barley, etc., swell so much when they are 
cooked. Your chestnuts swell when you boil them from the same 
cause. 

You will be surprised to learn that starch, though so different 
from wood, is composed of the same elements, carbon, hydrogen, 
and oxygen, and that, too, in the same proportions. It is deposit- 
ed in those parts of the plant where it can be used for food, the 
grains or seeds, and other fruits, as the tubers of the potato-plant. 

Sugar is another substance which is found in many plants. All 
fruits that are sweet have sugar in them. Besides this, there are 
some plants which are designed by the Creator to make sugar for 
the use of man ; of these the principal is the sugar-cane. Then 
there is the sugar-maple and the sugar-beet. Much sugar is ob- 
tained from the sugar-maple in the northern parts of this country. 
On the Continent of Europe, especially in France, the sugar-beet 
is largely cultivated for the manufacture of sugar. 

Sugar, like starch and wood, is composed of carbon, oxygen, 
and hydrogen, but not in the same proportions. Although we 
can not make sugar by mixing these ingredients together, any 
more than we can wood or starch, yet this is done in plants. The 
sugar-cane makes sugar for us out of charcoal and water, as I have 
told you wood is made. Much of the charcoal or carbon is taken 
from the air by the leaves, while the water comes up from the 
ground by the roots. The long, broad leaves, shaped much like 
corn-leaves, are spread out to the air to suck in, by their little and 
numberless mouths, the carbon from the air, so that there may be 



STARCH AND SUGAR. 198 



How sugar is obtained from the cane. Difference between cane-sugar and grape-sugar. 

enough of this material for making the sugar. Now as the car- 
bon in the air comes in part from the breath of animals, it may be 
that some of the carbon in some of the sugar that you have eaten 
may have come from your lungs. If so, a long way did it fly, on 
the wings of the wind, to the South, to get to the cane-leaf that 
drank it in. 

In obtaining sugar from the cane, the juice is first pressed out 
between heavy iron rollers. This juice is then cleared mostly of 
its impurities, and is boiled down to such a degree that the sugar 
will crystallize as it cools. While this crystallization is going on, 
there is a draining off of a sirup, and this is molasses. The sugar 
crystallizes in grains, and is the common brown sugar. Farther 
purification is required to make it into white sugar. 

There are different kinds of sugar. The two most important I 
will notice — grape-sugar and cane-sugar. Grape-sugar is that 
which is in grapes and in sweet fruits generally. Cane-sugar is 
that which is in sugar-cane and other plants that are evidently 
designed by the Creator to manufacture sugar for our use. The 
cane-sugar has much greater sweetening power than grape-sugar, 
and therefore is more valuable. It requires almost three tea- 
spoonsful of grape-sugar to sweeten as much as a single teaspoon- 
ful of the cane-sugar. 

The difference in composition between these two kinds is that 
the grape-sugar has more of oxygen and hydrogen than the cane- 
sugar ; or, because oxygen and hydrogen are the two ingredients 
of water, some chemists say that grape-sugar has more water in 
it than the other. 

Though we can not take carbon, and oxygen, and hydrogen. 

N 



194 STARCH AND SUGAR. 



Sugar made from saw-dust. 



and make them into wood, or starch, or sugar, we can make sug- 
ar out of either starch or wood. What! you will perhaps ex- 
claim, make sugar out of saw-dust ? Yes, exactly so. It can be 
done by oil of vitriol, water, and heat. Every five pounds of some 
kinds of wood may be made to give us in this way four of sugar. 

The process is as follows : The saw-dust is first moistened with 
a little more than its weight of sulphuric acid or oil of vitriol, 
and is left to stand for about twelve hours. It is now nearly 
dry ; but, on pounding it in a mortar, it becomes liquid. Some 
water is added, and it is boiled. The sugar is now formed. 

The explanation of its formation is this. In the saw-dust there 
are certain quantities of carbon, oxygen, and hydrogen. But 
there is not so much of the oxygen and hydrogen as there is in 
sugar. What needs to be done, then, in order to make the wood 
into sugar, is to add some oxygen and hydrogen, letting the car- 
bon be just as it is. This is exactly what the sulphuric acid does. 
It forces some of the water, or the oxygen and hydrogen that 
compose it, to unite with the carbon in the saw-dust, and so sug- 
ar is made. 

But the sugar is not alone. It is a sirup ; that is, there is wa- 
ter mixed with it. Besides this, the sulphuric acid is there also. 
This acid does not become a part of the sugar. It only forces 
some of the water to unite with the carbon of the wood. The 
acid itself is unchanged, and there it is mingled with the sirup. 
It would not do to let it remain, for you know how biting an acid 
it is. The way in which it is taken out of the sirup is a good ex- 
ample of chemical affinity. Chalk will take it out. See how it 
does this. Chalk is carbonate of lime, Now sulphuric acid likes 



STARCH AND SUGAR. fc 195 



Rag-sugar. Changing starch into sugar. A singular fact. 

lime better than carbonic acid does. It therefore takes the lime, 
and the carbonic acid flies off. The sulphuric acid forms with 
the lime sulphate of lime or gypsum. As this does not dissolve 
in water, the sirup is very easily separated from it. 

We now have the sirup. To get the sugar we have only to 
boil the sirup, and thus drive off the water into the air. 

Sugar can be manufactured from rags as easily as from wood ; 
for, as you learned in the previous chapter, the rags are nothing 
but wood in a certain form. 

The process of converting starch into sugar is essentially the 
same, for starch has the same composition as wood, as you learned 
in the first part of this chapter. But what is the sugar that can 
thus be made out of such cheap materials as saw-dust and rags ? 
It is not the cane-sugar, which is so valuable, but the grape-sug- 
ar. If we could manufacture cane-sugar in this way, we should 
not need to depend so entirely on the sugar-cane for our supply. 

See how singular it is that grape-sugar is formed instead of 
cane. To form the cane-sugar the sulphuric acid would have to 
force the water to unite with the carbon to only one quarter the 
amount which must be added to make the grape-sugar. It would 
seem that it would be easier to make the less quantity unite with 
the saw-dust than the greater. But no one has ever yet discov- 
ered any way of doing this. If any one could make such a dis- 
covery, and so manufacture cane-sugar out of saw-dust and rags, 
the patent would make him richer than the richest man now liv- 
ing, or perhaps the richest that ever lived. 

In England and on the Continent of Europe, where sugar is 
not as cheap as it is in this country, there has been a great deal 



196 STARCH AND SUGAR. 



Sugar in fruits. Sugar made into wood in plants. 

of cheating done by making this rag and saw-dust sugar, and 
mixing it with the sweeter cane-sugar. In England there is a 
law forbidding the manufacture of the grape-sugar. 

I have told you that there is sugar in all sweet fruits, but there 
is not sugar in them at first. They are either tasteless or acid, 
and become sweet as they ripen. Before they ripen there is 
starch in them, and this changes into sugar. Some of the acid 
also changes into this substance. 

Though we can make wood into sugar, we can not turn sugar 
into wood. This is done, however, in plants. Suppose we have 
a sugar-maple that has not been tapped by any one, what be- 
comes of all the sugar that is in it in the spring ? Does it stay 
there locked up for some one to get next spring? If it does, 
what a quantity of sugar there will be for him, for he will have 
all that is made in two springs. But the sugar does not all stay 
there as sugar. It circulates about in the tree, and helps to make 
leaves, and bark, and wood. This seems strange to you. But 
that sugar should be turned into wood is no more strange than 
that wood should turn into sugar ; and yet this last I have told 
you that we could effect with heat and oil of vitriol. And when 
we come to look into the whole matter, it is not so strange after 
all, for wood and sugar are both composed of the same things, 
carbon, oxygen, and hydrogen. The proportions only need to 
be altered to change the one into the other. 

We see the same change of sugar into wood in other vegeta- 
bles. Thus the sugar-beet and turnip are sweetest when gather- 
ed early. If allowed to remain growing too long, the sugar is 
changed into wood, and they become, therefore, tough and taste- 



STARCH AND SUGAR. 197 



How to make sugar-charcoal. 



less. So, also, if grass be left to grow too long, the starch and 
sugar in it turn to wood, and the hay is not as sweet and nutri- 
tious as it would have been if gathered earlier. 

We can make charcoal from sugar as we do from wood, for it 
is composed of the same elements that wood is. We can do it 
simply by heating the sugar ; but a prettier way to do it is this : 
Put a tablespoonful of strong sirup, made with loaf-sugar, into a 
tumbler set in a large plate, and pour upon it a little good sul- 
phuric acid. The acid sets free the charcoal, producing consider- 
able heat. This makes a brisk bubbling up, even over the sides 
of the tumbler. After the tumbler gets cool, pour the contents 
into the plate, and you have a specimen of sugar-charcoal. 

Questions, — What is said of the abundance of starch in plants ? Mention some 
of the vegetable substanees in which it is found. What is arrow-root ? what sago ? 
How can you obtain starch from wheaten flour ? What sort of a substance is starch ? 
What effect has boiling upon it? What is said of the composition of starch? 
Where in plants is it deposited ? What is said of the presence of sugar in vegeta- 
bles ? What is the composition of sugar ? What is said about the making of sugar 
in plants ? What about your breath furnishing sugar-making plants with carbon ? 
How is sugar obtained from the sugar-cane ? What is molasses ? What are the 
two kinds of sugar, and how do they differ ? What is their difference in composi- 
tion ? What is said of making sugar from wood and starch ? Describe the process 
of making it out of wood. Explain the chemistry of the process. How, now, is the 
sulphuric acid got rid of? How is the dry sugar obtained from the sirup ? What 
is said of making rags into sugar ? What of making sugar from starch ? What 
kind of sugar is made from these substances ? What is said of not being able to 
make cane-sugar in this way ? What of the manufacture of grape-sugar in Europe ? 
What is said about the formation of sugar in fruits ? What about the change of 
sugar into wood in the sugar-maple ? What about the same change in vegetables ? 
What is said of sugar-charcoal ? 



198 GLUTEN. 



Nitrogen in all animal substances. Animals must have it in their food. 



CHAPTER XXX. 

GLUTEN. 

You see that vegetable substances are made mostly of carbon, 
oxygen, and hydrogen ; but animal substances, flesh, skin, hair, 
nerves, etc., are made of these same three things, but with another 
added, viz., nitrogen. It is this gas that makes the great distinc- 
tion between animal and most vegetable substances. No animal 
substance was ever found that had no nitrogen in it. 

It is the nitrogen that gives the peculiar strong odor which we 
smell whenever any animal substance is burned. Wood, cotton, 
linen, etc., give out but little smell when burned, but let any wool- 
en thing, or hair, or leather be burned, and the odor is disagree- 
able and strong, and it is very much the same in all these cases. 

As all substances which are peculiar to animals have nitrogen 
in them, there must, of course, be some nitrogen in their food, for 
without this they would droop and die. It is the food that makes 
the blood, and the blood, as you learned in the Second Part of the 
Child's Book of Nature, is the building and repairing material of 
the body. You can see, then, that if no nitrogen is furnished to 
the blood, one of the four great materials for building and repair- 
ing will soon be spent. The body will, therefore, in a little time, 
show this great want, and get out of repair. And, if it remain so 
long, it will die. To repair the body without nitrogen would be 
very much like repairing a brick wall without brick, filling up 
breaches in it with mortar alone. 



GLUTEN. 199 



How animals get their nitrogen. Gluten. What it does to bread. 

Now you can readily see where some animals get that part of 
their building and repairing material which we call nitrogen. 
Lions, tigers, clogs, cats, etc., eat animal food, and there is nitro- 
gen always in that. But how is it with horses, cows, sheep, etc. ? 
Where do they get their nitrogen? They eat no animal food, 
and the vegetable substances that I have told you about, wood, 
starch, and sugar, have no nitrogen in them. There is a plenty 
of nitrogen all around them in the air, ar*l they breathe it con- 
tinually into their lungs. Do they get it in this way ? No, not 
a particle of the nitrogen gas that goes into the lungs gets into the 
blood. The oxygen that goes into the lungs with the nitrogen 
enters the blood, but the nitrogen does not. It comes out of the 
lungs exactly the same as when it went in. Neither does a particle 
of nitrogen go into the body of animals through the skin, though 
the skin is bathed in it all the time. 

How, then, do the vegetable-eating animals get their nitrogen ? 
I will tell you. You remember that, in telling you how to obtain 
starch from wheat flour, I said that there was a substance left in 
the linen cloth ; it is mostly a substance which we call gluten — a 
very glutinous or sticky substance. This portion of the flour con- 
tains nitrogen. While the starchy part is composed of carbon, 
oxygen, and hydrogen, this is composed of these and nitrogen 
united with them. 

It is the gluten of the flour that gives firmness to bread. If it 
were composed of starch alone the bread would be very crumbling. 
It is for this reason that rice griddle-cakes so readily break when 
there is not enough flour mingled with the rice. The gluten of 
the flour is needed to hold together the starchy rice. 



200 GLUTEN. 



Albumen. Casein. Nitrogenous and carbonaceous substances. 

There is another substance in the flour that has nitrogen in it. 
It is called albumen, from the Latin word albus, white. It is like 
the white of egg, and is really about the same thing. There is 
but little of it in the flour compared with the gluten. 

In the grain of wheat, then, we have three substances, starch, 
gluten, and albumen. There is much more of starch than of glu- 
ten, and the albumen is very small in amount. 

There is another substance that has nitrogen in it, which is 
found in many vegetables. We call it casein. It is nearly the 
same thing as the cheese which is contained in all milk, and which 
makes the curd. There is a great deal of this substance in vege- 
tables that grow in pods, as peas, beans, etc. 

The three substances in vegetables that furnish animals with 
nitrogen are, then, gluten, albumen, and casein. They are called 
nitrogenous substances. The most abundant of them is gluten. 
There is a great deal of this in the grains which are used so ex- 
tensively for food — wheat, rye, buckwheat, barley, oats, Indian 
corn, etc. 

Starch and sugar have no nitrogen in them, and carbon is their 
most important element. They are said, therefore, to be carbona- 
ceous substances, in distinction from the nitrogenous. Now these 
substances can not support life for any length of time alone. 
Some dogs which, by way of experiment, were fed upon nothing 
but starch and sugar, languished and died. It was for want of 
nitrogen. 

There is another class of substances, found both in vegetables 
and animals, which are carbonaceous, and have no nitrogen in 
them. They are the oils and fats. 



GLUTEN. 201 



Importance of gluten as nutriment. 



It is the nitrogenous substances in our food that build up and 
repair the body. Of what use, then, are starch, sugar, and the 
fats ? Their use is chiefly, if not wholly, to keep up the heat of 
the body. They are a part of the fuel, which is burning up every 
where with the oxygen that is in the blood, as you learned in the 
chapter on Animal Heat. 

The power of an article of food to nourish the body or promote 
its growth is supposed to depend on the amount of nitrogen there 
is in it. Eice is not very nutritious, because it contains a great 
deal of starch and very little gluten. The common grains, as 
wheat, rye, etc., are among the most nutritious vegetable articles, 
for there is much gluten in them. There is a great deal in the 
coverings of the grains, which, broken up, make the bran. There- 
fore bread made from bolted flour is not as nutritious as that 
which is made from the unbolted flour. Peas and beans are very 
nutritious, because they contain so much of that nitrogenous sub- 
stance, casein, or vegetable cheese. Cabbage is one of the most 
nutritious of vegetables, for it has even more gluten in it than 
the grains ; and cauliflower has a still greater supply of it than 
the cabbage. 

There is some gluten in leaves and grass, but not so much as in 
the grains. The horse, therefore, though he may do pretty well 
upon hay alone when idle, must have some kind of grain when 
he is worked. The wear and tear of the muscles in working 
makes a good supply of nitrogenous food necessary for repair. 
The camelopard, with his long neck, lives by browsing upon the 
leaves of trees. But if he worked, like the horse, he would re- 
quire some food richer in gluten. 



202 GLUTEN. 



Food of the laboring man. How bread is 4t the staff of life." 

For the same reason, the food of a laboring man should be 
richer in gluten than that of a man who lives at his ease. In 
the repairing that his muscles require after the wear and tear of 
labor, it will not do to supply only food that is composed of car- 
bon, and oxygen, and hydrogen, with very little or no nitrogen. 
There must be a good quantity of nitrogen in his food, for this 
is quite as essential as the other materials. If the laborer, there- 
fore, should live chiefly on rice, as in China, or on potatoes, as is 
often the case in Ireland, the machinery of his body would not 
be well repaired, and he would become weak. He must have 
such food as bread and meat, with his potatoes, rice, etc., in order 
to get enough nitrogen for growth and repair. 

' We need to have mingled together the two kinds of food — that 
which is for building and that which is for fuel. It is for this 
reason that the fuel-food, pork, goes well with the building-food, 
cabbage. 

Those articles in which the two kinds of food are mingled to- 
gether are peculiarly good articles. Thus bread is so good that it 
is called the staff of life. Still better is it when we add to it the 
fatty carbonaceous substance, butter. Milk is such a combination 
of the nitrogenous and carbonaceous substances that it is a com- 
plete food by itself, as shown by the fact that children often live a 
long time on this article alone. 

I have told you that all animal substances have nitrogen in 
them, and that most vegetable substances do not. Still there are 
some vegetable substances that do contain nitrogen. Why do 
they contain it? It is for the very purpose of supplying it to 
animals. Animals must have it in their structures — in their mus- 



GLUTEN. 203 



How nitrogen is provided in plants for animals. 



cles, nerves, bones, skin, brain, etc. But vegetables do not need 
it in their structures. Wood does very well without it, though 
bone and muscle can not. As, then, vegetables do not need it in 
their structures, Providence does not put it there, but makes it go 
into parts of vegetables where animals can readily get at it, and 
use it in their food. It is for this purpose that there is so much 
of it deposited in various grains for the use of man and other an- 
imals. 

Questions. — Of what are most vegetable substances composed? What compose 
animal substances? What distinguishes animal from most vegetable substances? 
What is said of the odor of animal substances in burning ? What is said of the ne- 
cessity of having some nitrogen in the food of animals ? In regard to what animals is 
it very plain where they get their nitrogen ? What is said about the vegetable-eaters 
not getting it from the air ? What is said about gluten ? What about the gluten 
in bread ? What about rice cakes ? What is said of albumen ? What of the three 
substances in the grain of wheat ? What is said of casein ? What are nitroge- 
nous vegetable substances ? Which is the most abundant of them ? What are car- 
bonaceous vegetable substances ? What is said of their power to support life ? What 
is said of oils and fats ? Of what special use are starch, sugar, and the fats ? Upon 
what does the nourishing power of substances depend ? What is said of the grains 
in this respect ? What of unbolted flour ? What of peas and beans ? What of 
cabbages and cauliflowers ? What is said of animals being able to live on grass ? 
What of the camelopard ? What of the necessity of nitrogenous food for the labor- 
ing man ? What about having the two kinds of food mingled ? What is said of 
bread? What of milk? What is said, in conclusion, about nitrogen in animals 
and vegetables ? 



204 FERMENTATION. 



The change produced in fermentation. 



CHAPTER XXXL 

FERMENTATION. 

In the two previous chapters I have told you about some sub- 
stances which are found in vegetables — starch, sugar, gluten, etc. 
In this chapter I shall tell you about some substances which are 
made from these by man. 

You have heard the word ferment often used, but have you 
ever thought exactly what it means ? When cider is first made, 
it is the mere juice of the apples. It is not fermented. It works 
or ferments afterward. So, also, wine is the fermented juice of 
grapes. In making it, the juice has worked or fermented, as the 
juice of apples does in turning to cider. Wine is made in the 
same way from other fruits, as currant, gooseberry, etc. When 
people use the word wine alone, it is understood as meaning 
grape- wine. When other wines are spoken of, the name of the 
fruit from which it was made is always given. 

What is done by the fermentation ? What is the change that 
is produced ? It is a change in the proportions of carbon, oxy- 
gen, and hydrogen, of which the substances that ferment are com- 
posed, or, rather, it is a change in one of these substances. The 
substance which is changed is sugar. All those liquids which 
become intoxicating drinks by fermentation are composed chiefly 
of su^ar dissolved in water, having a flavor given to it by the 
plant from which it comes. Thus the change produced in the 
juice of apples is only in the sugar that is in it. The water in 



FERMENTATION. 205 



How alcohol differs from sugar in composition. 



which the sugar is dissolved is not changed at all, neither is that 
which gives the peculiar taste to cider in distinction from other 
intoxicating drinks. So, also, grape-juice is sugar dissolved in 
water, with a flavor peculiar to the grape, and it is the sugar only 
that is changed in the fermentation. 

Notice now what the change produced in the sugar is. The 
sugar, so sweet to the taste, is changed into a fiery substance call- 
ed alcohol. It is so fiery that it must be diluted before it can 
be drank. In the strongest wine there is three times as much 
water as there is alcohol ; more than half of the strongest brandy 
is water ; in common beer only the one fiftieth part is alcohol. 

But I have not yet told you precisely what the chemical change 
is which fermentation produces in the sugar. Sugar is composed 
of carbon, hydrogen, and oxygen in certain proportions. It is 
the change in these proportions that turns the sugar into alcohol. 
The alcohol is composed, as sugar is, of carbon, oxygen, and hy- 
drogen, but their proportions are altered. It is just as calomel 
and corrosive sublimate differ from each other, the proportions 
between their ingredients, chlorine and mercury, being different, 
as noticed on page 162. It is also as the difference is made be- 
tween the laughing gas and the biting nitric acid. 

In the change of proportions, nothing is added to the sugar to 
turn it into alcohol. Something, on the other hand, is taken 
away. Some of the carbon and some of the oxygen of the sugar 
leave it, forming carbonic acid gas, which flies off into the air, if 
it be permitted to do so. The alcohol lias as much hydrogen as 
the sugar from which it is formed, but has less carbon and oxy- 
gen. 



206 FERMENTATION. 



Sugar divided into alcohol and carbonic acid. Yeast. Fermentation of bread. 

You see that the fermentation produces two things from the 
sugar — alcohol and carbonic acid. The sugar is divided or split 
into these. 

What produces this change in the sugar? Does the sugar 
change of itself ? No ; the change in the sugar is caused by some- 
thing else. If you make a solution of sugar in perfectly pure wa- 
ter, it will never turn into alcohol. Something must be added to 
the solution to effect this change. If you put in a little yeast, 
this will do it. But how ? Does the yeast unite with any thing 
in the sugar to form the alcohol, as oxygen unites with iron to 
form rust, or with potassium to form potash? No; it simply 
forces the sugar to separate into two things, carbonic acid and al- 
cohol. The yeast does not become a part of either the carbonic 
acid or the alcohol, just as the sulphuric acid, in changing wood 
into sugar (page 194), does not become a part of the sugar. It is 
merely the instrument by which the sugar is split into two parts, 
and is itself unchanged. 

But we do not put yeast into the juice of the grape to turn it into 
wine, or into the juice of the apple to turn it into cider. How, 
then, is the alcohol formed in them ? There is some gluten in 
these juices, and this becomes yeast, and so produces the ferment- 
ation. Either one of the nitrogenous substances, gluten, albumen, 
or casein, may act as a ferment. Common cheese may be used, 
for this is but a form of casein. 

The fermentation of bread is really the same thing with the 
fermentation which produces intoxicating drinks. The yeast 
turns the sugar that is in the dough into alcohol and carbonic 
acid, and these two together swell out the hollow cells which you 



FERMENTATION. 207 



Champagne wine and bottled cider. Making alcohol from barley, rye, etc. 

see in the bread. But you will ask what becomes of the alcohol. 
This flies off in vapor in the oven, and escapes into the air. In 
some large bakeries, in Europe, an attempt has been made to 
catch this vapor and condense it, so as to save the alcohol ; but it 
has not been very successful. 

In uncorking bottles of Champagne wine and cider there is a 
great escape of gas, making a lively foam. This gas is carbonic 
acid gas. It is made in the bottle by fermentation, and, so long 
as the liquid is confined by a tight cork, the gas is imprisoned 
there among the particles of the liquid ; but, the moment the 
cork is loosened, the gas escapes. In order to have this gas pro- 
duced, the liquid is put into the bottles before the fermentation is 
finished. A part of the process, therefore, goes on in the bottle, 
producing the gas. The same thing is true of bottled beer. 

The production of alcohol from the grains, barley, rye, etc., and 
from potatoes, is different from its production from apple-juice 
and grape-juice. In the articles which I have mentioned there 
is a great deal of starch and but little sugar, and this starch must 
be first changed into sugar before alcohol can be produced. Thus, 
in making beer from barley, the first thing is to make as much as 
we can of the starch in the barley into sugar. It is done in this 
way : The grain is moistened and left in heaps ; it sprouts, and, 
in doing this, much of the starch is turned into sugar, so that the 
barley has a very sweet taste. The malt, for so this sugared bar- 
ley is called, is now dried, and, after being bruised, is put into the 
boiler with water ; after boiling sufficiently, the liquor is drawn 
off into vats. It is now a sugary solution, and, the yeast being 
added to it, produces the alcohol from the sugar, just as it does 



208 FERMENTATION. 



The fermentation that produces vinegar explained. 



from the sugar of grape-juice in making wine, or that of apple- 
juice in making cider. When the mixture is boiling, the hops 
are put in to give the bitter flavor. 

So, also, in making whisky from the potato, the starch must 
first be converted into sugar. 

As alcoholic liquor is produced from the fermentation of a sug- 
ary solution, so vinegar is produced from the fermentation of an 
alcoholic liquor. The change which is effected in this case is the 
addition of oxygen to the alcohol, forming acetic acid, the acid of 
vinegar. As iron-rust is oxydized iron, and potash is oxydized 
potassium, so acetic acid is oxydized alcohol. If we leave a bar- 
rel of cider with its bung-hole open, it gradually becomes vinegar, 
because the oxygen of the air comes to the alcohol in it and ox- 
ydizes it. 

It is not the whole of the cider that is changed. As, when 
apple-juice turns to cider, it is only the sugar in the juice that is 
changed, so, when the cider becomes vinegar, the change is only in 
the alcohol. This turns to acetic acid, and what we call vinegar 
is only a little of this acid diffused through considerable water, as 
noticed on page 122. 

As the sugar will not change of itself into alcohol, so the alco- 
hol will not change of itself into vinegar ; there must be a fer- 
ment or yeast to produce this fermentation as well as that which 
forms alcohol. In making vinegar from cider in the common 
way, the work is done by the same gluten that was in the apple- 
juice and turned it into cider. 

Sometimes vinegar is manufactured in a rapid manner. It is 
done in barrels, as seen in Fig. 56. The barrel is represented in 



FERMENTATION. 209 



A quick way of making vinegar. 




Fig. 56^ t h e gg Ure as being open, that you may understand 
the arrangement. A mixture of alcohol and wa- 
ter, having a little yeast in it, is put into the ves- 
sel 5, and is allowed to drip from it through small 
holes in the bottom. The barrel is filled with 
loose shavings, which have been steeped in vine- 
gar. The air is admitted through holes c, c, c. 
Observe what the chemical operation of this is. 
The oxygen of the air unites with the alcohol as it trickles down 
through the shavings, and oxydizes it or turns it into vinegar. 
The vinegar is collected in a receiver, a. The object of the loose 
shavings is to spread out, as we may say, the alcohol, so that the 
air can come freely to every particle of it. 

The circulation of the air among the shavings is made very 
free by the heat which is produced by the process. This causes 
an upward current of air through the barrel, for the same reason 
that a fire in a fireplace causes an upward current in a chimney. 
Think a moment of the cause of this heat. The oxydation of the 
alcohol is a real combustion or burning, like all other oxydation, 
as stated in the chapter on Combustion. It produces heat, though 
not enough to cause a flame, for the oxydation is not rapid enough 
for that. 

In this chapter I have told you about some substances which 
never are found in plants, but which can be made out of certain 
vegetable substances. Thus, alcohol is never made in any plant, 
but man finds sugar in many plants, and out of that makes alco- 
hol. Then out of this he makes the acid of vinegar, ether, and 
some other substances. 

O 



210 FERMENTATION. 



Alcohol made by decomposing sugar. How alcohol, acetic acid, and ether differ. 

Now, as you can not make wood by mixing in any way its in- 
gredients (page 186), so you can not make alcohol out of its in- 
gredients. The only way to make it is to decompose sugar. So, 
also, you can not make the acid of vinegar, acetic acid, by mixing 
up its components. It is composed, like alcohol, of carbon, oxy- 
gen, and hydrogen, and it differs from alcohol only in having 
more oxygen in it. It is made, therefore, by adding the required 
quantity of oxygen to the alcohol. Ether, another quite common 
substance obtained from alcohol, differs from it only in having 
less oxygen and hydrogen, the carbon being the same in both. 

Questions. — About what kind of substances am I to tell you in this chapter? 
What is said about cider and wine ? What kind of change is produced by fer- 
mentation ? What substance in the fermenting liquids is changed ? What kind of 
a substance is formed from it ? In what is the sugar changed ? Give the compar- 
isons mentioned. What two things are produced in the change, and how ? How 
can you show that the sugar does not change of itself? In what way does yeast 
change it ? Give the comparison about sulphuric acid. How is the change pro- 
duced without yeast in making cider and wine ? What takes place in the fermenta- 
tion of bread? Explain the effervescence of bottled cider, Champagne, etc., when 
the cork is drawn ? Why is it that the gas collects in these liquids ? In making al- 
coholic drinks from barley, rye, etc., what change must first be produced ? Explain 
the making of malt. How is the alcoholic liquid made from this ? What is said of 
making whisky? How is the making of vinegar somewhat like the making of al- 
cohol? What is done to the alcohol to change it to acetic acid? What other 
changes is this like ? How is the oxygen added to the alcohol in cider ? How 
much of the cider is changed ? How much acetic acid is there in vinegar ? What 
effects the change in the vinegar fermentation ? Describe and explain the quick 
mode of making vinegar. How is the air made to circulate very freely among the 
shavings ? How is the heat causing this produced ? What is said of the substances 
noticed in this chapter ? How do acetic acid and ether differ from alcohol ? 



VEGETATION. 211 



Difference between a plant and a crystal in their growth. 



CHAPTEE XXXII. 

VEGETATION. 

Every plant comes from a seed. When the seed is put into 
the ground, a root shoots downward into the earth, and a stalk 
shoots upward into the air. 

Observe how the root and the stalk are made. They are not 
made as the crystals are. Particles are not laid on layer after 
layer, as in the growth of a crystal. There is no life in a crystal, 
but there is in the seed. It is this life that forms the plant, and 
it has its own way of doing it. As it builds the stalk and root, it 
forms channels or tubes as it works along ; but there are no such 
tubes in a crystal. 

Through these tubes the sap goes every where in the plant. 
This is true of every plant, from the smallest to the largest. 
Look at some very large and high tree. The life in a little seed 
began that. It pushed up the stalk a little higher and higher, 
making tubes in it all the while ; and now that it reaches up so 
high, the sap goes up from the very ends of the roots, in these 
tubes, out to the very ends of its myriads of leaves. 

Let us see now of what the seed from which all this comes is 
composed. It is mostly starch and gluten. But both of these sub- 
stances are insoluble. Of what use, then, can they be in growth, 
when they can not be carried up in the sap that circulates in the 
tubes ? Unless they can be rendered soluble they can be of no 
use — they must remain just there in the seed. But just exactly 



212 VEGETATION. 



How the plant gets its carbon, oxygen, and hydrogen. Where its nitrogen comes from. 

this change is produced in them. As the seed becomes moist, 
some oxygen is absorbed, and by this means the gluten is made 
soluble, and the starch is changed into sugar, which you know is 
soluble. So as fast as the channels are made in the up-shooting 
plant, the sap, with gluten and sugar dissolved in it, mounts up in 
them. 

You see now the explanation of the formation of sugar in the 
sprouting seeds of barley in preparing it for the making of beer, 
as described on page 207. 

But all this is merely to set the plant a going. When the little 
root is formed, and the stalk reaches the air and puts out leaves, 
the seed is all done with. Its gluten and starch are used up, 
and the plant now gathers all its materials for growth from the 
soil and the air. It must have carbon, oxygen, hydrogen, and 
some nitrogen. As you have before learned, it obtains from the 
air a large part of its carbon, taking it in at every pore in its 
leaves. Its oxygen and hydrogen it gets mostly from the water 
that comes into the mouths of the roots. 

From whence comes the nitrogen that it wants ? It may want 
considerable, for it may be a plant that has gluten in its fruit or 
seeds. At any rate, it wants some for its leaves. 

There is a plenty of nitrogen all about plants, for four fifths of 
the air is nitrogen. But, though their leaves are bathed in it all 
the time, though it is at the very door, as we may say, of every 
little pore, yet not a particle of it enters. All the nitrogen which 
the plant gets comes up from the ground. There are various sub- 
stances there that supply it. One is ammonia, which, you learned 
on page 97, is composed of nitrogen and hydrogen. There is a 



VEGETATION. 213 



Where the nitrogen is in plants. Lime, etc., in plants. What sap is. 

great deal of this substance in some manures, as you can know by 
the smell. The stronger is the ammonia smell in guano, the bet- 
ter it is. 

You have seen that carbon, oxygen, hydrogen, and nitrogen 
are the four grand ingredients in vegetables or plants. You have 
seen also that the three first of these compose the frame- work, 
the structure. There is no nitrogen in woody fibre in any of its 
forms, but this is found only in some of the fruits and juices. It 
is put there as a part of the food of animals. Plants gather up 
nitrogen from the earth, and deposit it within themselves for the 
use of man and other animals. It is deposited just where it 1b 
wanted. For example, there is none of it lodged in the stalk of 
wheat, but it is deposited in the seed or grain, so that we can have 
it in the flour with which we make our bread. 

There are some other things in vegetables besides those which 
I have mentioned, but in much smaller amount. I have already 
spoken of silica or flint as being in the stalks of grain and spires 
of grass (page 151). In many vegetables, as mustard and the 
onion, there is considerable sulphur. Then there are phosphorus, 
lime, potash, iron, etc. All these are carried up in the sap through 
the channels of which I told you in the first part of this chapter. 

Now think what sap is. Most of it is water, and this has dis- 
solved in it all the various substances which I have mentioned as 
being in plants. Water, then, not only furnishes the plant with 
oxygen and hydrogen, but it is the means by which the other 
substances needed by the plant are carried about in its channels 
or tubes to the very ends of the leaves. Some of the water re- 
mains in the plant, giving its oxygen and hydrogen to it to help 



214 VEGETATION. 



The quantity of water in plants, and its uses. 



form wood, starch, gluten, sugar, etc. But the largest part of it is 
breathed out into the air through the little pores in the leaves. 

The quantity of water that passes up through the channels in 
plants from the roots is much greater than most people suppose. 
We can get some idea of this by seeing a little how much passes 
off from the leaves. Some experiments have been tried in regard 
to this. It was found that in one case a single cabbage breathed 
out from its leaves into the air, in the course of twenty-four hours, 
nearly a quart of water. If so much comes from a cabbage, how 
much must all the leaves of a huge tree throw out into the air 
from all its leaves. 

In all juicy fruits there is much water. In the watermelon 
there is so much that it gives the name to the fruit. This is al- 
most all water, with a little sugar dissolved in it The cells that 
contain this juice are really wood, but very delicate, even more 
than those of the orange (page 189), and having a great deal of 
water mingled with it. 

It is the water in leaves and flowers that give them their soft- 
ness. You know how stiff the leaves of flowers are when pressed 
and dried by the botanist in his herbarium; it is because the 
water is all gone from their cells. 

You know how readily the stalks of grass and of grain bend 
before the wind, and then rise up again, giving the wavy motion 
which is so beautiful in a field of grain. This is because there is 
so much water in the cells and channels of the stalks ; but when 
the stalks of grain are dry, as you see in straw, they will not bend 
much. 

When wood is just cut it is said to be green ; that is, it is full 



VEGETATION. 215 



"What passes off from wood in burning. Composition of its ashes. 

of sap. As sap is mostly water, there is much water in the wood. 
This prevents its burning well ; but if it be left to lie in the air, 
this water passes off into the air, and so the wood becomes dry. 

When wood is burned there are ashes. These make but little 
bulk compared with the wood. There is a pound or two of ashes 
from a hundred pounds of wood. What has become of the re- 
mainder, the ninety -eight pounds of the wood? It has flown off 
into the air. As a large part of the wood comes from the air, so 
most of it, in burning, returns to the air. Much of what passes 
off is water, for even what we call dry wood contains considera- 
ble water. It passes off in vapor. Then most of the carbon of 
the wood, uniting with oxygen, flies off as carbonic acid. Some 
of the oxygen of the wood is disposed of in this way, and some of 
it unites with the hydrogen of the wood to form water, which 
goes off as vapor. If this were all, the smoke would not be visi- 
ble, for you can not see either vapor or carbonic acid gas ; but 
some of the carbon goes up in little particles, and these make the 
smoke a thing that you can see. 

What is really the composition of ashes? They are composed 
of potash, silica, lime, iron-rust, etc. These substances are found 
in different proportions in the ashes of different plants. Thus 
there is more of silica in the ashes of straw than in those of com- 
mon wood. There is much potash in the ashes of wood, and for 
this reason they are used for obtaining that substance for use in 
making soap, as noticed on page 131. 

Let us look a little more at what plants get from the ground to 
make them grow, and how they do it. They get all of the dif- 
ferent ingredients, except carbon, from this source. Most of this 



216 VEGETATION. 



An expedient in gardening. Living beauty from decay and death. 

they get from the air, but some of it comes from the ground. 
They get, then, from the ground all their oxygen, hydrogen, and 
nitrogen, and part of their carbon, and, besides these, small quan- 
tities of the various things which they need in addition, as potash, 
lime, iron, sulphur, phosphorus, etc. 

Now much of all these ingredients comes from the decay of 
plants. Every year great quantities of dead leaves and other 
parts of plants become a part of the earth, and help to form the 
plants of another year. You can make barren sand good rich 
earth by mingling with it decayed or decaying vegetable sub- 
stances. If, in a garden, you have a pit into which you throw all 
the weeds and small trimmings from trees, you can dig out from 
it, in two years of time, the richest kind of earth, the result of the 
decay. I have mentioned this because you are not too young to 
learn something about gardening. 

It is thus that decay and death furnish material for new life. 
The living beauty that feasts our eyes in the spring comes, to a 
great extent, from what fell to the ground and died the previous 
year ; and not only so, but that which in its putrefaction offends 
our sense of smell, becomes a part of the plants which, with their 
leaves and flowers, so delight our eyes, and the fruits which are 
so pleasant to our taste. The nitrogen, which is one of the in- 
gredients of the ammonia that you smell so strongly in the ma- 
nure of the stable, goes up the channels of the wheat-stalk, and 
helps to make the gluten of the grain, and as you eat it in the 
bread it helps to form the substance of your body. 

You see that there are few ingredients in plants, chiefly four, 
carbon, oxygen, hydrogen, and nitrogen ; but out of these, with 



VEGETATION. 217 



Composition of vegetable oils and acids. 



now and then a little of some others, are formed a vast variety of 
substances. I will notice a few of them. 

There are some substances that are composed of only two of 
the chief ingredients of plants, carbon and hydrogen. To this 
class belong the oils of orange-peel, lemon, and pepper. The oil 
of turpentine is also one, and that very singular substance so 
much used now for a great variety of purposes, caoutchouc, or 
India-rubber. 

Then there are some oils that are composed of three of the four 
grand ingredients of plants, viz., carbon, oxygen, and hydrogen. 
Among these are the oils of peppermint, valerian, anise, orange- 
flowers, rose-petals, etc. Camphor, also, is composed of these three 
ingredients. 

There are some oils that have considerable sulphur in them, as 
oil of mustard, onion, assafetida, etc. You know that a spoon, if 
left in mustard, becomes dark-colored. This is because the sul- 
phur in the mustard unites with the silver to form a sulphuret of 
silver. 

There are various acids in vegetables. These are composed of 
carbon, oxygen, and hydrogen, in different proportions. I have 
noticed some of these in the chapter on acids, as the tartaric, the 
peculiar acid of grapes, and the malic; the acid of apples, pears, 
and some other fruits. The only difference in composition be- 
tween these two acids is that the tartaric acid has a little more 
oxygen than the malic acid. 

There are many different coloring substances in vegetables, as 
indigo, the coloring matter of logwood, etc. They are composed, 
like the acids, of carbon, oxygen, and hydrogen, or of these with 
nitrogen. 



218 CHEMISTRY OF ANIMALS. 

Quinine, morphine, theine, and nicotine. 

There is an interesting class of substances brought to light of 
late years by chemists which I will just notice. There is quinine 
obtained from Peruvian bark, morphine from opium, theine from 
tea and coffee, nicotine from tobacco, etc. Nicotine is one of the 
most deadly poisons in the world. It takes less than a drop of it 
to kill a rabbit, if put upon his tongue. 

Questions. — What takes place when a seed is put into the ground? How are the 
root and stalk made differently from crystals ? What is said about the sap in plants ? 
What is said about a large tree ? Of what substances is a seed composed ? What 
change is needed in these, and how is it effected? What becomes of the seed? 
After the seed is gone, from what is the plant nourished ? What materials of growth 
must it have ? How does it get its carbon ? How its oxygen and hydrogen ? What 
is said about its needing nitrogen ? What about its not getting it from the air ? 
How does it get it ? What is said about guano ? Of what elements are the struc- 
tures in plants made ? Where in plants is nitrogen deposited, and for what pur- 
pose? Mention some other substances that are in some plants? What is sap? 
What is said of the uses of the water in sap ? What of the quantity of water that 
passes through plants ? What of juicy fruits ? What of water in leaves and flow- 
ers ? In the stalks of grass and grain ? In wood ? How much of wood that is 
burned becomes ashes ? What becomes of the rest ? Give the particulars. Why 
is smoke visible? What substances are in ashes? What do plants get from the 
ground? What is said of decay as furnishing materials for growth? What can 
you do profitably with weeds in a garden ? What is said of putrefying substances ? 
What of the ammonia in manure ? What is said of the formation of all the variety 
of substances in plants ? Which "two of the grand ingredients of plants form some 
of these substances ? Mention some substances composed of these ? What oils are 
composed of three of the grand vegetable elements ? What is the composition of 
camphor ? What oils have considerable sulphur in them ? What is said of vege- 
table acids? What of coloring substances? From what is quinine obtained? 
From what morphine ? From what theine ? From what nicotine ? What is said 
of nicotine ? 



VEGETATION. 219 



Amount of water in the blood. Other ingredients of the blood. 



CHAPTER XXXIII. 

CHEMISTRY OF ANIMALS. 

The blood is to an animal what the sap is to a vegetable. The 
sap is water, having dissolved in it whatever is necessary to the 
growth or building up of the plant ; and so the blood is water, 
having dissolved in it whatever is necessary to the growth or 
building up of the animal. 

About four fifths of the blood in us is water ; that is, in every 
five pounds of blood there are four of water. You will, of course, 
want to know what substances are dissolved in this ; that is, what 
make up the other fifth of the blood. They are carbon, oxygen, 
hydrogen, nitrogen, chlorine, sodium, potassium, magnesium, iron, 
phosphorus, and sulphur. 

These substances, you see, are elements, not compounds. But 
they do not appear as elements in the blood. They are united 
together in various ways. For example, the iron is united with 
some of the oxygen, forming oxyd of iron, and some of this oxyd 
is united with phosphoric acid, making phosphate of iron. So 
most of the chlorine is united with the metal sodium, forming 
common salt, giving to the blood a saltish taste. Then we have 
phosphorus, oxygen, and calcium united together to form phos- 
phate of lime, of which, you learned on page 148, there is so much 
in the bones. About one third of that part of the blood which is 
not water is albumen. This is the same substance as white of 
egg, or the albumen which you learned on page 200 is found in 



220 CHEMISTEY OF ANIMALS. 

How different substances get into the blood. Chemistry of the stomach. 

many vegetables. This is composed of the four grand elements, 
carbon, oxygen, hydrogen, and nitrogen. 

How do all these different substances get into the blood ? They 
come from the food that we eat. All that part of the food which 
will serve to nourish the body is drank up by little mouths in 
the stomach, and is put into the blood and becomes a part of it. 
It is exactly as the little mouths in the roots of a plant suck up 
from the earth what is proper to go into the sap. The fact that 
the root of a plant and the stomach of an animal thus perform 
similar duties is fully illustrated in Chapter IV. of the Second 
Part of the Child's Book of Nature. 

But all the substances that are in our blood are not always in 
our food. How is it, then, that the blood is always supplied with 
them ? It is because the food contains what these substances are 
made from. There is some chemistry done in the stomach. It is 
a sort of chemical laboratory. Great chemical changes are pro- 
duced there in what is put into it. For instance, you eat, in one 
way and another, considerable sugar ; but there is no sugar in the 
blood. How is this? Is all this sugar lost? No ; it is all used, 
but it does not go into the blood as sugar ; it helps to make some 
other things that go into the blood. 

There is salt in our blood, and there is salt in our food. Here 
we have a substance that is not altered by the chemistry of the 
stomach, as sugar is, but goes into the blood as salt. 

There is one substance, all of which does not getinto the blood 
from the food ; a part of it goes in by the lungs as we breathe. 
This is oxygen, the lung-food that I told you about on page 16. 

All the different parts of the body, as I told you in Chapters I. 



CHEMISTRY OF ANIMALS. 221 

How the body is built. Expedient for making bright scholars. 

and II. of the Second Part of the Child's Book of Nature, are made 
out of the blood. For this purpose the blood, containing all these 
different substances that I have mentioned, goes or circulates 
around every where in the body; and just what materials are 
wanted for building are used just where they are wanted. For 
example, where it is necessary to make bone, the materials for 
bone are taken from the blood, and are arranged so as to make 
the bone of the right shape. Phosphate of lime is one of these 
materials, as I told you on page 219. This is in the blood, all 
ready for use. 

So, where there is nerve to be made, those materials are taken 
from the blood of which nerve is composed; and the same is 
true of all other parts of the body. Once in a while there is a 
mistake in this matter. For instance, bony substance is formed 
in some part where it is not wanted, as in the arteries or in the 
heart. But, generally, every thing is put in the right place. 

Brain and nerve are composed of a variety of substances — a 
white fatty substance, a red fatty substance, albumen, phospho- 
rus, sulphur, potash, lime, magnesia, etc. Phosphorus is an essen- 
tial ingredient in brain ; that is, the brain can not do without it. 
I have heard it recommended as a good thing for persons that 
study to eat freely of eggs, because they contain considerable 
phosphorus. I do not believe, however, that this would make a 
bright scholar out of a dull one. Something else besides egg- 
eating is needed for that. 

In hair, feathers, bone, and nails there are sulphur and silica, 
or flint, mingled with the other ingredients. 

There is iron in the blood, It is in the substance that gives 



222 CHEMISTRY OF ANIMALS. 

Iron in the blood and in various parts of the body. Milk a very compound food. 

the red color to this fluid. Very little of it is to be found ever 
in any of the solid parts of the body. There is none in the 
nerves, though it is common to speak of persons who have much 
firmness of character as having iron nerves. There is a very lit- 
tle of it in the hair, helping, with the silica or flint, to give it 
strength. Exactly of what use it is in the blood we do not know. 
When persons are pale and weak they have not enough of it in 
the blood, and we give them medicines that have iron in them. 

You have seen what a variety of substances there is in the 
blood. Now when one eats a variety of food, it is easy to see 
how all these various substances are furnished to the blood. But 
how is it with a child that lives only upon milk ? Can there be 
mingled together in that white fluid all the substances that I have 
mentioned ? If they were not there would be something missing 
in the building up of the body. If, for example, there were no 
phosphate of lime in milk, the infant living on milk would have 
its bones grow, but they would be soft, and would bend very easi- 
ly, for it is the phosphate of lime that makes them hard and stiff. 
Milk contains this, and all the other substances that are required 
for the growth of the body. It contains all the nutritious sub- 
stances which you can gather from meats and vegetables united 
together. 

There are exactly the same elements or ingredients in milk that 
there are in blood ; but they are not all put together in the same 
way, and so the milk is different from the blood. Milk is made 
from blood, and blood is made from milk, and they are really only 
two different forms of the same thing. The milk of the cow is 
made from her blood by a chemistry which we do not understand, 



CHEMISTRY OF ANIMALS. 223 

How chyle is made and supplied with oxygen. 

and when we take it into our stomachs the chemistry there changes 
it back again into blood. How the iron is kept in the milk, and 
is prevented from coloring it red, as it does the blood, we do not 
know. 

No matter how many different articles we eat, the nutritious 
part of them all, which is taken and put into the blood, is a whit- 
ish fluid very much like milk ; it is called chyle. This fluid is 
separated or extracted from all the meat, and potato, and rice, and 
squash, and turnip, and cabbage, etc., etc. ; and it contains all that 
is needed to form bones, teeth, brain, skin, nerves, muscles, nails, 
hair, etc., with one single exception — I mean the oxygen which 
it gets from the air in the lungs. The chyle goes to the lungs in 
the blood to get its supply of oxygen ; and now it becomes a part 
of the blood, and is ready to go to any part of the body to nour- 
ish it. 

Questions. — Give the comparison between sap and blood. How much of the blood 
is water ? What elements are in the blood ? Mention some of the combinations of 
these in the blood. What is said of the albumen in the blood ? How does the blood 
get all the substances that are in it ? Give the comparison between the stomach of 
the animal and the root of the plant. How is it that there are some substances in 
the blood that are not in the food ? What is said of the sugar that we eat ? What 
of salt ? What is said about lung-food ? What is said of the circulation of the ma- 
terials for building different parts of the body ? What of making bone ? What of 
making nerve ? What are the substances in brain and nerves ? What is said of eat- 
ing eggs ? In what animal structures are there flint and sulphur ? What is said of 
iron in the blood ? WTiat is said of the expression iron nerves ? What is said of 
milk ? How is milk like blood ? How does it differ from it ? What is said of 
chyle? 



22-1 CONCLUDING OBSERVATIONS. 



Comparative abundance of the elements. 



CHAPTER XXXIV. 

CONCLUDING- OBSERVATIONS. 

It may be well, in this concluding chapter, to look back a little 
upon the ground that we have gone over. 

The whole world is built up chiefly out of a few elements. I 
have told you, in Chapter XV., that there are a little over sixty 
elements, and of these about fifty are metals. Most of these exist 
in small quantities. A few of them are very abundant, as iron, 
calcium, sodium, aluminum, copper, lead, etc. But the most abun- 
dant substances in the world are not metals. They are oxygen, 
carbon, nitrogen, hydrogen, silicon, sulphur, chlorine, etc. Near- 
ly, if not quite one half of the world is a gas, oxygen. And the 
four grand elements used in the making up of the earth are oxy- 
gen, carbon, hydrogen, and nitrogen. Three of these, you see, are 
gases. Water, that liquid which is every where, and in almost 
every thing, is composed of two of them. All living substances, 
vegetable and animal, are essentially composed either of three of 
them or the whole four. 

One thing is true of oxygen which is not true of any other ele- 
ment, viz., that it forms combinations with all the other elements. 
With most it unites very readily, with some eagerly ; but there 
are some, as gold, silver, etc., with which it will not unite unless 
it be forced to do it, as you learned in Chapter XXVII., and when 
it is united with them a very little suffices to make it part com- 
pany and fly off. 



CONCLUDING OBSERVATIONS. 225 



Some of the combinations of oxygen noticed. Its activity as an agent. 

Let us look at a few of the combinations which, oxygen forms. 
It forms with hydrogen the most abundant of all compounds, 
water. Mixed with nitrogen and carbonic acid gas, it forms the 
most abundant of all mixtures, the atmosphere. It forms, with 
the metals oxyds, a very numerous class of substances. It forms 
acids with nitrogen, sulphur, phosphorus, chlorine, silicon, etc. 
That singular acid, silica, is one of the most plentiful hard sub- 
stances in the earth, being in the granite and many other rocks, 
and constituting, for the most part, all the sand of the land and 
sea, and a large portion even of the fertile earth. Then we have 
oxygen in all the potash and lime, and in their carbonates ; the 
carbonates of lime in the forms of limestone, and chalk, and mar- 
ble, being very abundant substances, sometimes forming even 
mountains. Besides all this, oxygen is one of the chief ingredi- 
ents in all living substances. 

But you see the importance of this element not only in its 
abundance, but also in its active agencies. It is no laggard in 
the chemical movements which are every where going on ; it is a 
lively, busy agent. It is the grand supporter of combustion. It 
keeps every fire and light burning, and the quick explosions of 
gunpowder and many other substances are produced by it. It 
maintains the life of all animals by entering the lungs continual- 
ly, and it conveys away carbon from their bodies to the leaves of 
plants by uniting with it to form carbonic acid. It rusts the met- 
als wherever it can get hold of them, and it has such an affinity 
for some of them that they can never be found except in the em- 
brace of oxygen. 

The changes in the forms of ijjatter from solid to gaseous or 

P 



226 CONCLUDING OBSERVATIONS. 

Changes in the forms of matter. 

liquid, and the reverse — changes in which oxygen commonly is 
so busy — are very wonderful when we look into them. Thus, in 
the burning of wood, the oxygen of the air unites with the carbon 
and hydrogen of the solid wood, forming the gas carbonic acid 
and water, which flies off with the gas in vapor. In one hundred 
pounds of wood, as I have told you on page 215, we have com- 
monly but about two pounds of ashes. The ninety-eight pounds, 
which are water and carbonic acid, have flown off into the air. 
What becomes of them? Let us follow and see. The water 
gathers in the clouds to fall to the earth, or settles upon the 
ground in the form of dew. In whatever way it comes to the 
earth, it goes to work there again, and works chemically, for some 
of it finds its way into the roots of plants, and helps to form their 
substance by combining with carbon and nitrogen. That part 
of the ninety-eight pounds which is carbonic acid floats off to be 
drank up by leaves, in order to furnish carbon, by chemical oper- 
ations, to the plants and trees. The oxygen that has thus con- 
veyed, as we may say, the carbon to the leaves, returns again, in 
the air, to the lungs of animals ; and some of the carbon thus fur- 
nished to plants comes back also to animals in the food which 
they eat, to do again its chemical work in them. 

Many other examples of changes of matter back and forth from 
one form to another might be given, but this will suffice. 

When a solid becomes a gas, or a gas a solid, the change is a 
very great one. When a solid becomes a gas it occupies a vast- 
ly larger space, and the particles must therefore be much farther 
apart. When this change of bulk takes place suddenly a great 
effect is produced. It is this sudden change of bulk that gives 



CONCLUDING OBSERVATIONS. 227 

Expansions and condensations of matter. Fine division of the particles. 

such force to the explosion of gunpowder. On the other hand, 
when a gas becomes a solid there is a great condensation, or, in 
other words, the particles of the substance are brought much 
nearer together. For example, when oxygen unites with iron, 
and thus becomes a part of a solid substance, about twenty gal- 
lons of the gas are pressed, as we may say, into the small space 
occupied by a pound of the rust (page 93). The same enormous 
change in bulk takes place when the carbon in the carbonic acid 
of the air, taken in by the leaves of a tree, becomes so condensed 
as to form a part of the solid wood. 

In some of the changes which are going on in matter there is a 
very fine division of the particles. As you see charcoal burning, 
solid carbon is passing off into the air united with oxygen. The 
particles of the carbon you see in the solid charcoal, but when ' 
they pass off you do not see them. Why ? Because they are so 
finely divided. The division is so fine that not even the micro- 
scope can show them to you. So, also, if you examine the sap 
of grass, that feels very rough from the silica or flint that is on its 
surface, you can not find any particles of silica in it ; but they are 
there, for it is in the sap that the flint goes up from the ground to 
get to its place on the surface of the grass. The sap is smooth 
and limpid, for the flint in it is exceedingly fine, and its particles 
are wide apart ; but, deposited in the coating of the grass, the 
flint is rough, and scratches your finger, for the particles are there 
closely united together. So, too, the little iron that is in your 
blood is very finely divided, its particles being diffused evenly 
throughout that fluid as it circulates in your arteries and veins. 

I have often, in the course of this book, spoken of the difference 



228 CONCLUDING OBSERVATIONS. 

Difference between compounds and their ingredients. 

between compounds and their ingredients. Thus oxygen, the gas 
that makes things burn, unites with another gas that itself burns, 
to form a substance which quenches burning. Water is unlike 
its components in other respects also. It is quite a heavy fluid, 
while one of its components, oxygen, is nearly as light as air, and 
the other, hydrogen, is the lightest substance known. So, also, 
that powerful liquid, nitric acid, is totally unlike the oxygen and 
nitrogen gases that compose it. Take another example of a dif- 
ferent character. Phosphorus is a very inflammable substance, 
and lime is a biting caustic ; but phosphoric acid, composed of 
phosphorus and oxygen, when united with lime, forms phosphate 
of lime, the mineral matter in our bones. One of the most strik- 
ing examples we have in common salt, which is composed of a 
gas that would kill you by suffocation if you should breathe it 
clear, and a metal that water will set on fire. 

I have occasionally noticed in this book the fact that a sub- 
stance may appear in different forms, perhaps wholly unlike each 
other. Thus carbonate of lime appears in the forms of chalk, 
common limestone, and the pure crystallized marble. Gypsum, 
or plaster of Paris, presents several forms, some of which are very 
beautiful. Carbon is one of our most wonderful examples, for 
nothing can be more unlike than charcoal, blacklead, and the di- 
amond. There is no substance, perhaps, that appears in so large 
a number of different forms as wood, as you learned in Chapter 
XXYIII. All this variation in form must be owing wholly to 
variation in the arrangement of the particles, as the proportions 
of the ingredients are not varied. 

In this variation, the differences in character are much increased 



CONCLUDING OBSERVATIONS. 229 

Elements united in different proportions. Frame-work of chemistry. 

if the proportions of the ingredients are varied. You know how 
different calomel and corrosive sublimate are, yet they are made 
of the same elements, chlorine and mercury, but in different pro- 
portions. The five compounds of oxygen and nitrogen are very 
different from each other, the contrast between the exhilarating 
gas and the nitric acid being as great as could possibly be con- 
ceived. But the most wonderful examples are furnished to us by 
the chemistry of life. Wood, starch, gum, sugar, oils, perfumes, 
coloring matters, poisons, etc., how unlike, and yet they are all 
made of three elements, a solid and two gases. The same may be 
said of the variety of compound substances in animals, which are 
all composed of the four grand elements. It is thus that the Cre- 
ator shows, in the chemistry of life, the greatest power in produc- 
ing a vast variety of substances from a very few materials. 

The frame-work, as we may call it, of chemistry is quite simple. 
Most of it may be thus marked out : 

Oxygen forms with the metals oxyds. \ These, uniting 

Oxygen forms with carbon, sulphur, nitrogen, > together, form 
phosphorus, chlorine, etc., acids. ) salts. 

Sulphur forms with the metals sulphurets. 

Chlorine, iodine, etc., form with the metals chlorides, iodides, etc. 

Then, in the chemistry of life : 

Some vegetable substances are made of oxygen, carbon, and %- 
drogen. 

Other vegetable substances, ) are made of oxygen, carbon, hydro- 

And all animal substances, ) gen, and nitrogen. 

There are some substances that are not included in this plan. 
This is the case with one of the most important and abundant 



230 CONCLUDING OBSERVATIONS. . 

"Water a singular substance. How matter circulates. 

substances in the world, viz., water. This would be included if 
we should call it an oxyd of hydrogen ; but this hardly seems 
to be proper, as hydrogen has nothing of the character of a 
metal. 

Water, then, appears to be a substance by itself, having no re- 
semblance to any other substance or class of substances. It is not 
like the acids, or oxyds, or salts. It has no decided character in 
taste or smell, and yet it has a great deal to do with a vast varie- 
ty of chemical operations every where. 

This leads me to remark that much of the matter in the world 
is constantly circulating back and forth between animals and veg- 
etables and the earth, and in this circulation it is all the while 
changing. The grand means by which this circulation is carried 
on are air and water. These are every where in motion, and they 
carry with them a great many substances wherever they go. For 
example, the air takes the carbon from our lungs, and carries it 
aloft for the leaves to take in, and brings back to our lungs the 
oxygen that the leaves breathe out. As an example of the agen- 
cy of water in this circulation, you have seen how it dissolves the 
carbonate of lime from the rocks and the earth (Chapter XXII.), 
and carries it into the sea for the shell animals to construct their 
shells from it. So, also, water brings the silica to the grasses and 
grains, that it may be sucked up by the roots. In these and many 
other ways, air and water are ever busy circulating substances, 
solid as well as liquid and gaseous, in every direction ; and they 
thus have more influence than any other agents in carrying on the 
grand chemical operations of the world. They are not only con- 
tinually changing themselves, but they produce changes in other 



CONCLUDING OBSERVATIONS. . 231 

Chemistry does not destroy matter, but only changes it. 

substances by bringing them together so that they can act upon 
each other. 

The world, as you have seen by what I have told you in this 
book, is emphatically a world of change ; and in the changes that 
take place there is no loss, no destruction. When things burn 
up, as we express it, there is no destruction of any substance, 
but there is # merely change from one form to another, and what 
seems to vanish in air soon reappears in the solid forms that are 
growing up all around us. So, when decay takes place, there is 
no loss of a single particle of matter, but there are only chemical 
changes bringing about new combinations and arrangements of 
the particles of the decaying substance. Chemistry is at work 
every where, not destroying, but pulling to pieces only to rebuild 
again, and it does the latter quite as readily and rapidly as it does 
the former. 

Questions. — How many elements are there? How many of them are metals? 
Name some of the most abundant of them. What are the most abundant of all the 
elements ? What are the four chief elements ? Which of them is the most abun- 
dant ? What is said of it ? Give what is said of some of its combinations. What is 
said of its activity as an agent ? State in full what is said of the changes that take 
place in the combustion of wood and in consequence of it. What is said of the ex- 
pansion and the condensation of matter in chemical changes ? Give the illustrations 
of the fine division of matter in chemical changes. What is said of the different 
forms in which the same substance may appear? How is it when the ingredients 
are the same, but the proportions are varied? Give the illustrations. Give the 
frame-work of chemistry as stated. What is said of water ? Give in full what is 
said of the circulation of matter. What is said of the changes that chemistry is ef- 
fecting in the world ? 

THE END. 



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